Eratic Login Behavior

Sorry for the double post earlier (can't seem to get rid of the duplicate?).

I'm still having problems that appear to involve user logins, sessions, cookies...not sure exactly what. The errant behavior is much like what was described in the discussion at http://drupal.org/node/470538, but there's no resolution to the issues posted there.

In my case users are complaining (not too loudly) that their logins are lost even over short periods of time (like cookies aren't working) but only some of the time; and I have seen this sporadic behavior too. I've also seen instances where I'm logged into my Drupal web site (http://igo.tamatoledo.org) and when I jump to the forums I have to login again. At other times I'm able to jump back and forth without having to login again.

I've never taken the time to try and understand how cookies and sessions work... never really needed to before.

Can anyone explain (briefly...or in detail) how the logins between a Drupal site and it's phpBB3 counterpart are supposed to work? Or, can anyone tell me what the user table data (I'm assuming table 'users' in Drupal and 'phpBB3_users' in phpBB) is supposed to look like in a properly functioning Drupal/phpBB integration?

FYI... In my case I run both Drupal and phpBB3 from a single database. Drupal version is 6.15 and phpBB is 3.06 (I believe).

Thanks.