Hi, I finally installed the beta! Great!
Some bug reports on your XHTML at the ubbthreads.php page from the Golive6 error checker:
there is somewhere a "table cellpadding" without a value.
"&" (and maybe other reserved characters?) are allowed in the ubbt-board titles but are not converted to & so they show as & which is not correct xhtml
"äöüÄÖÜß" and other language specific letters are "hard-written and not converted in html: If the forum is maintained with a MAC I suppose the letter is unreadable with a PC? (although I cannot test it, I run MAC only.

) - I found this problem with forum names and also descriptions.