I'm not sure if this has been directly addressed yet, or if anyone else has encountered it but...
When I try to login using the SMF Mambo login module, it prompts me to "please fill in the username and password fields", which I already did.  After this happens, the User Menu appears as if I have logged into Mambo, but the SMF menu does not appear, and it still says "Welcome Guest" on both the SMF Mambo login module and the Forum itself.  This continues after I try it again.  However, I CAN log in from the Forum login box, and everything works correctly. 
So basically, when trying to Login from the SMF Mambo module, it logs me into Mambo but not the Forum, but it works both ways if I login from the Forum itself (which is obviously less convenient and more confusing to my users).  Any help or other people with similar problems?

I have this problem as well.
I believe this is a known issue and it is being looked into.

having the same problem... no fix yet?