Um, your AP doesn't lower as far as I know, however, I think I know what may have happened.
You probably posted things the Moderators found spam, and deleted it, lowering your points. If this was the case, then if you don't want to lose any more, post better Game Comments(you might easily get a Merit when doing this remember), Forum Posts, or keep what you say on the Profiles down to useful and non-spam type of stuff.
If the points do go down, that doesn't really make any sense at all, unless it is to keep inactive members from clogging up the Leaderboards perhaps... Hope that helps =D
