The battle with SAV continued as the uninstallation of the retail version of Norton AV left a rogue plug-in left on my PC at home
It turns out that my botched upgrade of Norton meant that it left the office scanning plug-in left on my system. Any time that I tried to open a document in Word or Excel, Office threw its toys out of the pram:
Word: The file is inaccessible and cannot be opened (or something like that)
Excel: The file
So it turns out that if you do happen to get this problem, then you might want to try and check the knowledge base at Symantec. You should see an article about what registry keys need to be deleted. Although, this didn’t work for me on the first attempt. Excel worked and Word barfed. However, I left the PC alone for a week and it seemed to resolve the issue itself. While switched off no less.