I finally found a fix to a reoccurring problem I've been having with Sharepoint Designer 2007!

Problem

For some unknown reason certain files in Sharepoint Designer 2007 would show they were checked out when they were actually checked in. This would cause me big headaches when I would edit a file and try to check-in or publish - an error dialog box would pop up saying "Cannot perform this operation. The file is no longer check out or has been deleted." - which meant Sharepoint Designer was pretty much useless. "Recalculate Hyperlinks" didn't help.

The only way I could get Sharepoint Designer to recognize the true state of the file was to rename the file, or I could go in to "Manage Content and Structure" via the browser and check the file out, but I had to remember to keep the file checked out if I published a major version. What a headache…

Resolution

delete the site's web cache located here: %UserProfile%\AppData\Local\Microsoft\WebsiteCache