I think there may be a bug with the live word count on the post writing screen.
If you write any number of words, delete (eg. backspace) one or more words and then write one or more words, the word count is now wrong. As long as you keep writing and deleting words, it will get worse.
If you "Save and Continue Editing" your post, the word count is corrected.
Can anyone else confirm this?
Tested on Firefox 2, IE 7, and Opera 9 on Vista.