Ive checked the HTML code generateed by PHP. I only see one thing wrong on the code. the href on the anchor tags on html is set to "catrow.U_VIEWCAT" which make on sense watsoever on HTML. My best guess us that U_VIEWCAT is a contant defined in PHP that is not anymore present.
I can only speculate what the error is... i need to look at the code to actually pin point the error and for you tell me exactly to what extent did you customized the forum.