... the title is not strictly correct. I can "save-as" over the top of the same file via the UNC path. Yes, that's weird. Trying to save-as over the top of that again via the mapped path triggers a sharing violation, as you would expect.
I get this in AutoCAD and Excel. It is intermittent and happens rarely.
Sometimes in Excel the file will open and then, about 10 seconds later, I get a dialogue saying the file is available as read-write. Um, thanks - that's the way I opened it.
Client is Windows XP sp3. AV is Symantec Endpoint. Neither was my choice.
Server is Windows Server, 2008 (not R2 - that would be modern), I think.