I opened this question just a few minutes ago and it had Edit (1) on it. I clicked on this Edit link to see the edits and got the screen in the image below. Unfortunately, that was it: I couldn't approve or reject it (I maxed out my review votes for today), but I also could not dismiss the popup, as it was opened too high (?) and scrolling didn't help either. I suspect this is a bug - or am I missing something? I know this worked in the past, but I don't think I ever tried doing this after exhausting my suggested-edit votes review quota for the day.

EDIT: this is firefox 16.0.1 on linux.

Update 2: Here's another screenshot - from today. From what I have seen so far, it appears that the lightbox popup appears a specific number of pixels above the actual "edit" link. If the edit is on a first post on the page and the post is rather short, then the top of the popup is above the top of the browser page and thus the popup cannot be closed. If the edit is for a long post or on one of the answers, then there's sufficient room above to scroll up to see the top of the popup. Firefox has been updated to 16.0.2 - the issue still persists.