Although this is for v1.3.1, I'm guessing it also applies to 1.4beta, since I didn't read that it was addressed.
Normally after a certain period of inactivity, OG logs the user out and presents a log in box (see attached pic).
However, I've noticed that it only logs the user out if they are in the following modules:
tasks
weblinks
contacts
email
notes
And it does not log me out while in the following modules:
overview
documents
Time
Reporting
calendar
Tested in FF 3.0.9
cheers