Peerblock not updating
Copy the contents of the spreadsheet to a new one, and deleted the old one (it wasn't a particularly important spreadsheet, thankfully), and everything was fine.
I can only assume that somehow the file had become corrupted.
What I found to be the problem was the formula and the fact that I surrounded numbers with quotes.
If you don't see anything at all on screen, especially if you think the updates might have been installed completely but could be the cause of whatever you're experiencing, see our How to Fix Problems Caused by Windows Updates tutorial instead.
If there's any wonder after that long, take a look at your hard drive activity light.
You'll see either no activity at all (stuck) or very regular but very short flashes of light (not stuck).
I opened this spreadsheet, checked that this was still working and autoupdating with current installation of MS Excel and any new automatic office updates (which it did work with), and then just reopened the original spreadsheet. I ran into an issue where some cells weren't calculating.
I checked all the normal things, like cell type, auto calculation, etc...