coppermine-vbulletin session problem

[evitu]

I have the following issue after having bridged coppermine and vbulletin:
the bridge seems to be ok, but when I check option "remember me" in log-in process, after a bit (in the same session) during gallery's navigations I lost my log-in in the coppermine, while in vbulletin I remain logged.

I have already tried to clean up my cookies but the problem remain.

Any suggest?

Coppermine install: http://www.scientificomanfredonia.com/cpg/
Forum install: http://www.scientificomanfredonia.com/forum/
Coppermine version: cpg1.4.19
Forum version: vbulletin 3.7.1
Test user account: test_tmp/test_tmp

BridgeManager settings:
Forum URL:  http://www.scientificomanfredonia.com/forum
Relative path to your BBS's config file:  ../forum/
Use post-based groups?:  0

Thanks in advice.

[Nibbler]

vb probably deletes your session after a while for being inactive (in the forum), and the bridge file does not support 'remember me'.

[evitu]

Thanks for the answer. 
I will try to send a null ajax request on each gallery's page in order to keep alive sessions.