[TYPO3-linux] problem with editing several content elements in backend

[Amir Nahvi]

i have a new opensuse server and there about 40 websites with typo3.

on my old server i had no problems, but now there is a new problem.

when i am logged in backend and try to edit more than 3 contentelements on 
the same time it logg me out automaticly as soon as i click on save button 
or close and save button after editing the elements.

does anyone knows that problem?
it must be a problem from server, cause on the old server i could do it, and 
on my windows computer i can do it too on localhost.

please help me!