Lightbox for product images has stopped working.

Using version 1.4. For some reason the lightbox or slimbox effect has stopped working. Now when you click on a product thumbnail it loads the image beneath the web page and regardless of the size of the first image, it loads in the size of the second. Any help or ideas about this would be appreciated. I've checked to see if I might have modified a file that could have caused this, but it was working yesterday and I haven't made any modifcations since before yesterday. Thanks.

Just in case anyone else runs into this problem, I found the cause. It was in the product.css file. I found a line that did not have the closing "}." Why it had worked for so long I cannot say.