I'm having the same issue. 

JSMF 2.0.2
SMF 1.1.4
Joomla! 1.0.13

The install says the user tables are sync'd, but no one can login when viewing the site. 

Users log into the site using their CB logins, which allows them to see the forums, however they aren't logged into the forums, and trying to do so logs them out of the main site.  Also, none of their site logins work for the forums when logging in through the site, but DO work when using the forums through their absolute URL.

Main site: www.rfi-eve.org
Forum site: www.rfi-eve.org/forums

I can assume the JSMF did in fact sync the user tables with SMF, however for whatever reason, the SMF bridge within Joomla! isn't letting people use them.  Go fig.

Still doesn't work.  I unpatched, uninstalled, and installed 2.0.2.1 and I still get the same problem.  The CSS matches that of the rest of the site much better, and people's profiles takes me to their CB profile, so I see what changes were made there.

However, logging into CB does not log me into SMF.  Trying to log me into SMF logs me out of CB (and doesn't log me into SMF anyway).

and then you patched again? Maybe you could check your index.php for any joomlahacks code.