I used to get that all the time when I had a 'gothic + alt' category, from the moment I joined Purstorm 'til I gave up and moved all the pics and deleted the category (just a few months ago.) It always jumped to second place no matter how I tried to arrange things. It's not happened since with any of my other categories. All I could possibly suggest that worked for me is move all your images out of the offending category that won't behave into a different one momentarily, then try moving them back into it? Good luck, I'd be kicking my monitor if it was still happening to me.