I had the same setup and had no issues with login.
However, I had other issues including improper 404 handling and poor CB URL optimization that were directly attributable to SmartSEF.
The SmartSEF project seems to have been abandoned by the developer. (Google for it.) So, I made the difficult decision to switch to sh404sef on a live site this week. Painful, but I'm glad I did as sh404sef seems to integrate with CB much better than SmartSEF does... And the developer is VERY active.
Good luck!