You usually get this error for one of two reasons. 

1)  Your script file doesn't match your solpartwebcontrols.dll version. 

I checked and this is not the case with you.

2) The html on your page is malformed.

Looking at your page, I can see that it looks like something is messed up.  For your footer on some of the forum pages is placed in the left pane.

What exactly is causing the error? 

The code looks for a particular SPAN on the page that is rendered server-side.  If it is not found, then you get the error and the menu involved will not render.

Hope this helps

Thanks you guys for the suggestions. Dare was right on the money, once I removed the 20 seconds cache period from the Advanced Settings page, it all seemed to work fine.

Once again, thanks for the help.