Guest user logged out and cannot log back in

[drewlander]

I have setup a user I call guest, that has the following permissions:
View Graphs
User Has Rights to Tree View
User Has Rights to List View
User Has Rights to Preview View

People can view graphs fine, however when they leave their browser open in cacti for about 15-30 minutes, they are unable to log back in, they have to clear their browser cache to log back in.
I do not have this problem as I am an administrator.

Is there a setting I am missing?
Thanks!