it looks like it works from the details page, just not from the results page.
when i view source of the results page, i see an onclick event that doesn't look right:
onclick=";progressformbutton = this"
<input type="submit" class="Tributecustom" value="Add to Cart" name="ProWaterParts_1_ATC" onclick=";progressformbutton = this">
i dont see this on the code for the page you sent?