It looks like search engine friendly URLs are the cuplrit. The redirect points to:

http://www.snowjapanforums.com/ubbthreads.php/ubb/cfrm

However, if you go to this url it works:

http://www.snowjapanforums.com/ubbthreads.php?ubb=cfrm

The reason is that all of your image src in the header are like thi <img src="image.gif"> So it's going to look in the current directory (which it thinks is /ubbthreads.php/ubb/cfrm) which obviously doesn't exist.

2 ways to fix this. Change your header include so you include the full relative url, ie <img src="/image.gif"> or <img src="/images/image.gif">.

The second is to disable search engine friendly URLs.