Login session problems...

Hi fellow Drupallers!

Situation
I have an intranet with many users. Partial login with LDAP partial with normal drupal accounts. Recently i have blocked some content for specific user roles (no i dont use organic groups). For keeping login sessions alive i installed the Remember me module. It should keep the login sessions for 4 weeks now.

My prob:
Many users within a certain domain use one Windows login. After that, they login with a normal Drupal account. This is one drupal account for like 30 users. This shouldnt be a problem (so i read on the forums).

Now when they login, they sometimes are logged out automaticly... So the sessions isnt saved for 4 weeks..

I hope this is clear enough! Hope Yall can help!

Thanks in advance!

Aeroniro