Edit: actually, re-reading your issue, it doesn't seem like a key error at all. I know exactly what would cause that issue... and it shouldn't be happening (though obviously is). When was the last time you did a clean install (you can keep your save files)?
I've never minded repeat reports, the alternative is that there might be something I miss (Or worse, a bug report that has slipped through the cracks), which is so much worse. So if you ever feel the inclination to report something, I will always do my best to check it out. The worst it can cost me is a couple of minutes and it might be something really important.
One of the most common bugs that happen in the guide are key errors, effectively a spelling mistake in a variables name. These are a lot more common than I would like...
So if you shoot me either a screenshot of the error or even just the line that says key error I'll do my best to fix it up.