Ran into a new problem with SharePoint Designer today. Not sure how I caused this to happen but several files were marked as checked out in SPD despite the fact that the files were not checked out to anyone in SharePoint. SPD would not allow me to check out the files, errored if I tried to check in the files, restarting SPD didn’t help, even rebooting didn’t help.
Turns out you have to clear a cache in the local app storage. The fix to this problem is to navigate to your local app settings WebSiteCache folder, which in Windows Vista is here:
From there just delete all the files or just the ones that correspond to your SharePoint site. When you restart SPD you may have to check in/out the files one more time, but after the warning message the file status will return to normal.
Thanks to Tom Puleo’s blog for the information