Solution (for me) to the "Thumbnails Not Enlarging" bug Answered
Just sharing what worked for me (sorry if posting it as it's own subject is against the rules, I do so so those with the issue will easily find this).
Adblock Plus is the culprit to our problems (as found by Kiteman, his find pointed me in the right direction). Simply updating your filter subscriptions will solve the issue.
In Firefox: click on Tools, mouse-over Adblock Plus, select Filter Preferences, click Actions and choose Update Filters. All that's left is to refresh the page and all should be fixed (it was in my case, mileage may vary).
I hope this helps you guys and gals who have this issue.