Interesting! I noticed the very same thing over the weekend with some buttons in a worksheet I've used for a few years, now. All they do is sort the worksheet on various columns, but they've suddenly stopped working—stopped doing anything at all, that I can see. I didn't think to try using <F5> on them, though.

I've an hypothesis that they actually stopped working when I switched to Excel 2010, only I didn't notice it because I don't use those buttons very much. By any chance would that fit your situation? I'm wondering whether I need only redefine the buttons to make them work. Maybe between the two of us we can figure this out and discover that the cause is the same for both of us.