Frameset/page does not exist

Has anyone seen this error message when a form has been open for an extended amount of time in a frameset?

Frameset “whatever” does not exist.

or

Page “whatever” does not exist.

The message appears when the user comes back later to finish the form and then clicks the send/save button. It’s almost like the form looses its association with the frameset.

I have multiple databases that I’ve seen this problem exist so any help would be greatly appreciated.