simple problem: mambo login/logout not working...... smf login/logout working

I'm using mambo 4.5.1b .
Linux server.
MOS-SMF 1.3.1

I've installed everything in the component. The syncing is a success (i made sure the email address all not clashing.)

I'm sure the logging in the mambo side is failling as:

1) when i use the normal mambo login, (not the smf-mambo) it doesn't have a logout button. However the who's "online module" mark that the user has logged in. When i proceed to the forum I am indeed login. However in the mambo front end, I can't access any "members-only" or "registered" modules/components/functions.

2) when i use the smf-mambo module, it acts exactly the same way as the above, except that I have a "logout" link now. However when i actually press log out, I am logged out from SMF but still logged in within mambo. The "logout" link is now not there, replaced by the usual "username" "password" input forms.

3) functionality in smf is flawless. When i try to login, it works when i log out, it goes back to mambo (again logged out in smf but not in mambo)

I'm sure i'm not logged out in mambo as the administrator controls shows that the users I "logged-in" under remains "logged-in" although i already infact "log out" using the "smf-mambo login form".

I have patched the index.php file. I then chmod it back for security. It remains patched. It's synced already. I can't see why it doesn't work. Is it compatibility with the login for 4.5.1b?