I'm using Excel 2000, and for no apparent reason the Tab button has mysteriously stopped working properly. Instead of moving 1 cell to the right it now moves me to the next of the 1st, 16th, 31st, 46th, 61st... column. CTRL+left or right does the same thing. CTRL+up or down seems to work properly. I've got Excel 97 on my machine as well and that seems to work fine.

Any ideas.