Go to an existing item, select "Add to a collection", pick an existing collection from the drop down menu, press "Add" => sad goblin appears.

Running with lazyserver to get more informative error message I get (two CRITICA rows added according to pythonsnake's suggestion for added debugging info):

Starting server in PID 32700.
serving on 0.0.0.0:6543 view at http://127.0.0.1:6543
2013-03-10 14:13:40,638 CRITICA [mediagoblin.user_pages.views] <class 'mediagoblin.db.models.Collection'>
2013-03-10 14:13:40,638 CRITICA [mediagoblin.user_pages.views] <type 'int'>
Error - <class 'sqlalchemy.exc.InterfaceError'>: (InterfaceError) Error binding parameter 0 - probably unsupported type. u'SELECT core__collections.id AS core__collections_id, core__collections.title AS core__collections_title, core__collections.slug AS core__collections_slug, core__collections.created AS core__collections_created, core__collections.description AS core__collections_description, core__collections.creator AS core__collections_creator, core__collections.items AS core__collections_items \nFROM core__collections \nWHERE core__collections.id = ? AND core__collections.creator = ?\n LIMIT ? OFFSET ?' (<mediagoblin.db.models.Collection object at 0x2b81910>, 1, 1, 0)
URL: http://saz.im:6543/u/sazius/m/58/collect/
File '/var/www/mediagoblin/lib/python2.6/site-packages/Paste-1.7.5.1-py2.6.egg/paste/exceptions/errormiddleware.py', line 144 in __call__
  app_iter = self.application(environ, sr_checker)
File '/var/www/mediagoblin/lib/python2.6/site-packages/Paste-1.7.5.1-py2.6.egg/paste/urlmap.py', line 203 in __call__
  return app(environ, start_response)
File '/var/www/mediagoblin/lib/python2.6/site-packages/Beaker-1.6.4-py2.6.egg/beaker/middleware.py', line 155 in __call__
  return self.wrap_app(environ, session_start_response)
File '/var/www/mediagoblin/mediagoblin/app.py', line 236 in __call__
  return self.call_backend(environ, start_response)
File '/var/www/mediagoblin/mediagoblin/app.py', line 216 in call_backend
  response = controller(request)
File '/var/www/mediagoblin/mediagoblin/decorators.py', line 224 in wrapper
  return controller(request, media=media, *args, **kwargs)
File '/var/www/mediagoblin/mediagoblin/decorators.py', line 48 in new_controller_func
  return controller(request, *args, **kwargs)
File '/var/www/mediagoblin/mediagoblin/user_pages/views.py', line 232 in media_collect
  creator=request.user.id).first()
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/orm/query.py', line 2181 in first
  ret = list(self[0:1])
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/orm/query.py', line 2048 in __getitem__
  return list(res)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/orm/query.py', line 2252 in __iter__
  return self._execute_and_instances(context)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/orm/query.py', line 2267 in _execute_and_instances
  result = conn.execute(querycontext.statement, self._params)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py', line 664 in execute
  params)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py', line 764 in _execute_clauseelement
  compiled_sql, distilled_params
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py', line 878 in _execute_context
  context)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py', line 871 in _execute_context
  context)
File '/var/www/mediagoblin/lib/python2.6/site-packages/SQLAlchemy-0.8.0-py2.6-linux-x86_64.egg/sqlalchemy/engine/default.py', line 320 in do_execute
  cursor.execute(statement, parameters)
InterfaceError: (InterfaceError) Error binding parameter 0 - probably unsupported type. u'SELECT core__collections.id AS core__collections_id, core__collections.title AS core__collections_title, core__collections.slug AS core__collections_slug, core__collections.created AS core__collections_created, core__collections.description AS core__collections_description, core__collections.creator AS core__collections_creator, core__collections.items AS core__collections_items \nFROM core__collections \nWHERE core__collections.id = ? AND core__collections.creator = ?\n LIMIT ? OFFSET ?' (<mediagoblin.db.models.Collection object at 0x2b81910>, 1, 1, 0)


CGI Variables
-------------
  CONTENT_LENGTH: '676'
  CONTENT_TYPE: 'multipart/form-data; boundary=---------------------------145476651317241088371037342262'
  CSRF_TOKEN: u'14123432470749457721'
  HTTP_ACCEPT: 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
  HTTP_ACCEPT_ENCODING: 'gzip, deflate'
  HTTP_ACCEPT_LANGUAGE: 'en,en-gb;q=0.8,sv-fi;q=0.6,sv;q=0.4,fi;q=0.2'
  HTTP_CONNECTION: 'keep-alive'
  HTTP_COOKIE: 'mediagoblin_csrftoken=14123432470749457721; mediagoblin_csrftoken=14123432470749457721; mediagoblin=c096c3693b3d407a8586a3c412afb3b9'
  HTTP_DNT: '1'
  HTTP_HOST: 'saz.im:6543'
  HTTP_REFERER: 'http://saz.im:6543/u/sazius/m/58/collect/'
  HTTP_USER_AGENT: 'Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20100101 Firefox/10.0.12 Iceweasel/10.0.12'
  PATH_INFO: '/u/sazius/m/58/collect/'
  REMOTE_ADDR: '82.181.107.174'
  REQUEST_METHOD: 'POST'
  SERVER_NAME: '0.0.0.0'
  SERVER_PORT: '6543'
  SERVER_PROTOCOL: 'HTTP/1.1'


WSGI Variables
--------------
  application: {(None, ''): <beaker.middleware.SessionMiddleware object at 0x27efdd0>, (None, '/mgoblin_static'): <StaticURLParser '/var/www/mediagoblin/mediagoblin/static'>, (None, '/mgoblin_media'): <StaticURLParser '/var/www/mediagoblin/user_dev/media/public'>, (None, '/theme_static'): <StaticURLParser '/var/www/mediagoblin/user_dev/theme_static'>}
  beaker.get_session: <bound method SessionMiddleware._get_session of <beaker.middleware.SessionMiddleware object at 0x27efdd0>>
  beaker.session: {'_accessed_time': 1362921220.6312571, 'user_id': u'1', '_creation_time': 1362921214.262624}
  paste.httpserver.thread_pool: <paste.httpserver.ThreadPool object at 0xc43d50>
  paste.throw_errors: True
  werkzeug.request: <Request 'http://saz.im:6543/u/sazius/m/58/collect/' [POST]>
  wsgi process: 'Multithreaded'
------------------------------------------------------------

After discussions in irc with pythonsnake this fix was tried and seemed to fix at least this problem:

diff --git a/mediagoblin/user_pages/views.py b/mediagoblin/user_pages/views.py
index dc56208..0036ded 100644
--- a/mediagoblin/user_pages/views.py
+++ b/mediagoblin/user_pages/views.py
@@ -227,7 +227,7 @@ def media_collect(request, media):
     # Otherwise, use the collection selected from the drop-down
     else:
         collection = Collection.query.filter_by(
-            id=form.collection.data,
+            id=form.collection.data.id,
             creator=request.user.id).first()
 
     # Make sure the user actually selected a collection

I encountered this because I've set my web browser (Iceweasel/Firefox 21) to store my MediaGoblin password and automatically fill it in when it deems appropriate.

Steps to reproduce

1. Go to "Change account settings".

2. Web browser automatically fills in "Old password" field, but leaves "New password" field empty (user that only wishes to change license setting will not notice this as it happens automatically).

3. Change license setting if you want (this seems to be optional).

4. Press "Save changes."

5. Log out and try to log in again: your old password doesn't work, the new password is the empty string. (Can be confirmed e.g. by trying to login with the piwigo plugin which allows empty password to be entered.)

The change account settings dialog should either warn of empty password, or simply assume the user does not wish to touch the password if it is left empty. (As was my case.)

When I'm running "./bin/gmg dbupdate" I'm getting this warning, which apparently isn't fatal, but a bit scary and annoying :-) According to joar it's because it is run without CELERY_CONFIG_MODULE being set.

/var/www/media/local/lib/python2.7/site-packages/celery-2.5.3-py2.7.egg/celery/loaders/default.py:64: NotConfigured: No 'celeryconfig' module found! Please make sure it exists and is available to Python.
  "is available to Python." % (configname, )))