I have exactly the same issue. I couldn't resolve the problem but did some diagnosis, so I wanted to share it with you.
1. The first user which is created using the django command line doesn't raise this issue.
2. The problem seems to come from the presence of the field "authusergroups_ptr_id" in the table "askbot_groupmembership". When a new user is created using the askbot interface, new groups are created and the "askbot_groupmembership" is populated with pointers to these groups. If you delete these pointers (entries) from the "askbot_groupmembership", then the save action works just fine.
I think, the reason why #1 works fine is that no groups and groupmemberships are created when the user is created with the manage.py commandline.
So, I think we should look at why these membership keys raise a problem. This seems to be happening in askbot/models/__init__.py during the creation of a new user but I couldn't figure out what the problem is.
Do you have the same issue on askbot alone, without integration? What is the version of the database and Django?
Yes. I deployed askbot as standalone app and still have this problem. Django 1.3.1 and Postgres 9.1.7. I suppose it connected with many to many relation between "auth_user" and "auth_group" (table auth_user_groups). When I deleted all records from table "askbot_groupmembership" user information updated without any exceptions.
Thanks for the info. Maybe this is related to the postgres version, we'll test on that.
Tested postgres 8.3 - same problem.
9.1.8 same problem