Application Timing Out

I have a strange problem where the application appears to be timing out. Once I authenticate and set the session variables, I can upload pictures just fine.

However - when a certain amount of time transpires, this no longer works. I'm unable to upload images or view images from the server via the file browser.

I thought the problem was related to sessions, so I changed the variable storage method to client vars, as we store them in the database instead of memory, and the time out is much longer.

However - I'm still seeing the same problem. Unfortunately, this results in support calls from our users who can't upload images all of a sudden.

I can't figure out if this is related to ColdFusion, or the application itself.

Help!

Thanks,

David