Uneven spacing between items... been up all night. (link to my website)

Hi. I just finally got around to finishing installation/customization of the now-superceded v1.2.7. It looks pretty much how I want it to except that the items are spaced unevenly and I can't figure out why. I've perused these forums left and right and can't find my answer.

Here's what it looks like: http://www.feralward.com/store/index.php?main_page=index&cPath=3

Notice how the first three items are closely spaced while the following aren't, and have a dividing line at the bottom. I was having this same problem yesterday when adding new products to the feralward category but if I did a refresh of the 'Product in Category: "Feral Ward" ' it worked itself out. Today it won't.

Can someone with more knowledge than I explain why? Or where/how I can fix it?

Many thanks.
YANNICK

Ok, I figured out that that space is an extra line added to the code of the dual pricing mod I installed. The items I'd listed before the mod didn't have this space and the new ones do. How do I remove that space? Or at least where can I start looking.

Again, if you visit:
http://www.feralward.com/store/index.php?main_page=index&cPath=3

and do SELECT-ALL (ctrl-A) you see where the extra space is.

Any help is much appreciated.
YANNICK