We've had one cat for about a year and got a new one in October.  They
survived through December with one box and no problems.

In January, we moved the location of the litter box.  The reason for
this was because we kept it in a back room that was cold and by keeping
the door closed, we'd spend less on heating.

Anyway, the older cat did not take to the move.  He started defacating
in other places but 99% of the time it was right next to, but not in
the box.  We've moved it three times so far (with sufficient time for
adjustment) and still no luck.  He will ocassionally defecate in the
box but usually doesn't.  He does, however, always urinate in the box.

We decided that maybe he developed some issue with sharing a box so we
put out another one, next to the first box but still no luck.

I don't think it's a clean box issue because we scoop at least once a
day.

Any suggestions?