[Simon Lloyd]

Where Lynne mentions caching, if you are using xcache you'll need to give each config a different setting not doing so can crash the memory or, as you are having, difficulties displaying things called in to a cache such as templates

As a test, change the folder name that your forum is in or change the database details in config.php to something ficticious, clear your server cache and then try and access your test forum see what issues you have, but before that i'd copy the database again and import it in to the test database again.