Randomly engaging NumLock considered irritating

Dear Fedora Core 6 X server: please stop randomly turning my NumLock on. It's getting really old by now, especially since I use a BTC-5100C mini keyboard and so turning NumLock on sprinkles numbers around my typing instead of the letters that I expected.

(It also makes various fvwm2 operations not fire, since I'm not hitting shift+alt+mouse button, I'm 'hitting' shift+alt+numlock+mouse button. I'd tell fvwm2 to ignore the state of NumLock entirely, except it currently serves as a useful cue to me that hey, NumLock got turned on again.)

Perhaps this is some accessibility feature that I am accidentally waking up, but it seems unlikely; I'm running in a bare session, without the usual Gnome or KDE stuff started up. Nor is there any apparent pattern for when it happens, although it happens fairly infrequently and I probably don't notice it right away when it does.

PS: this is unlikely to be hardware failure since it is happening on two machines, although both have BTC-5100C keyboards. (I really like them.)