Forum Moderators: open
If you go to File - Save As, you should get a prompt. Also, make sure you are working in a "Expression Web" and metadata is on (Site - Site Settings - General Tab (Manage the website using hidden metadata files).
Are your files saved on something like an external drive that has to spin back up after long periods of inactivity?
just wondering if it may be hardware related as opposed to the program causing the issue...