One reason that your post count may have receded is because, I had to delete the original What'ch Somkin' thread for February, last night. If you had a several posts in that string your count may have fallen.
The reason it was deleted is because when it exceeds 23 or 24 pages (circa 800 posts) it begins to push into the right hand column of the Main Forum page, and throws the design out of "whack"... (note the technical terminology)
So, to restore the page to its proper proportions we sometimes have to delete that one thread in particular.
Also, Cajunguy's supposition is applicable as well... on rare occasions.