In the past few days, I've noticed that the category display at the bottom of the page has been malfunctioning.

e.g. http://peswiki.com/index.php/PowerPedia:Joseph_Papp%27s_Noble_Gas_Engine

sometimes one of the categories is appended immediately (to the right, with no space) after the last item on the page

sometimes the box with gray background is absent.

I think I'm using 1.6, which has been very stable, with virtually no problems, for the past half year or so since upgrading.

any ideas as to what might be causing this?

Sterling