Don't ya just love it when that happens? I just went back and did a half-dozen trivial excercises with one of my databases without any problems, but you know it has to be something in particular that's borked. You think the CSS is just scrambled, or were your operations fubar also (I sure hope not- that would major suck!)?
As for DH up/down grading, for what it is worth, the phpMyAdmin instance I checked out is running version 2.6.4-pl3