mmm, if the path isn't working in the *new* location, I'm not sure there (make sure the folder is chmodded 777).
As for a redirector, this should work (this goes in a .htaccess file):
redirect 301 /ubbt/memberfiles http://www.yourdomain.tld/forum/memberfiles
redirect 301 /ubbt/memberfiles/ http://www.yourdomain.tld/forum/memberfiles/
If it doesn't work in your htaccess file in your web root, you could try putting one in your ubbt folder and set it as:
redirect 301 /memberfiles http://www.yourdomain.tld/forum/memberfiles
redirect 301 /memberfiles/ http://www.yourdomain.tld/forum/memberfiles/