Actually I find it's usually a good idea to ALWAYS try to know WHY things work because if you don't you'll find the disconnect eventually bites you in the ass. :/

If you've ever fiddled with the aim vector, up vector or world up vector options in the option box, remember that changed values will "stick" and then become the default for use anytime that you don't open the option window and edit those settings.

Again, as I suggested, the Aim Vector setting is almost certainly the issue. Changing the Aim Vector picks a direction in local coordinate space for the light that gets aimed at the target.

The Up Vector and World Up Vector settings control the orientation of the aimed object around the aim vector, so for a spotlight it probably won't matter what those settings are because it's circular and all orientations around the center axis amount to the same thing.

-- Mark