I tried bulk price editing yesterday.
My new prices seemed to be ok but the available sizes were duplicated.
Also, the preview thumbnails and dimensions changed from rectangle to square. (8x8, 10x10, 12x12 etc.)
I emailed support but of course with the world ending, and it being a weekend, I haven't heard anything back from them.
EDIT:
I just re-applied the bulk price change and all appears normal again.