I finally got around to upgrade my live server to 3.1.x and when I did I couldn't login. I had to go to my backup and fix. Why or how do I fix this problem? I had a similiar problem on my dev version but I only had host and admin accounts so it wasn't a biggy to just go into the db and fix.

This thread should answer your question: http://forums.asp.net/1060007/ShowPost.aspx - BTW, it will save you time in the future if you do a quick search before posting. This is a common problem and there are several posts about it. - Kind Regards - Rob

I think you probably have the same problem described in this post.  It seems to be a very common problem with people upgrading and not understanding some of the instructions properly. 

http://forums.asp.net/1051817/ShowPost.aspx