Customer always gets kicked back to login.php

[forbes28]

I am having a problem with a client. Cusotmers complain that they always get kicked back to login.php before they can do anything on the web site. In some cases, they always get kicked back to login.php. I cannot ever recreate the problem on any of my computers. Anyone had this problem before? Any solutions or anything to get me on the right path? I thought maybe it was a cookie or session issue, so here is my setup:

 

Session Directory /tmp

Force Cookie Use False

Check SSL Session ID True

Check User Agent True

Check IP Address True

Prevent Spider Sessions True

Recreate Session False