Internet Expense Receipts

When attaching a receipts, I select the file I want to attach and click "Apply".  When I do so, I can an error saying that my session timed out.  Why would this happen? I had an issue once before and what I would do is delete the current expense report, enter a new one and attach the receipts.  That would work fine but does not always work.  Is it a setting somewhere that needs to be looked at?