Office for Mac 2004 - Excel 11.5.8 - OS 10.5.8

All of a sudden, the number keys in the number pad move the active cell around in an unpredictable manner instead of entering data in the active cell. Further, an older anomaly is related, and that is the Enter key in the number pad moves the active cell to the right instead of down.

I could not find anything in Excel Preferences that addresses this, nor do I see anything on the keyboard that might trigger this change. However, the num lock light does not come on, so I'll have to figure out if it's active or not somehow. But that can't be the problem...

I opened a black document, the number keys entered numbers. I then reopened a document it was misbehaving on, and the number keys entered numbers! Does anybody know what was going on, and how I can fix it permanently?

In an unrelated glitch, Excel quit unexpectedly while I was working on a problem file. When I relaunched, the problems were still present.