Any type of caching on your server like xCache or memcache?

xCache, Lynne - should I turn it off on my test site?

Something I would also check. When you go into the Admin CP of your test site, take a look at what the links in your ACP are pointing to. Are they pointing to files in the test ACP, or your main domain ACP? Change the skin in your ACP. See if that change is reflected in your main domain's ACP. See if any of that helps narrow the problem down.

Hi Digital Jedi, thanks! All links pointing to the test site - where can I change the ACP theme?

vBulletin Options ? Admin Control Panel Options. It would be interesting to note if the ACP is also affecting the main board.

Jeeze, Digital Jedi, that killed our main site again!!!! Turned off xcache in both configs, and now everything is okay. I can change themes, page titles, etc - so what's going on?? Can I turn back on xcache for my main site? Thanks everyone!

I'm not as familiar with xcache as others might be, but if it really is chaching PHP pages the way it's supposed to, then it might be wise just to run it on the main site. Again, I don't know much about how it works, but if you have everything backed up, testing with the demo xcache off shouldn't be a problem. No reason why it would really need to be on, on the demo site. Because very few people will ever have access to it.

Thanks! So if I turn xCache back on, it won't screw up everyone's cookies again and log them out?

I can't say for certain. All I know is it's definitely not needed for the demo site. However, I couldn't say what changes were already enforced when they were both active. That's why I say you shouldn't proceed unless you have a fairly recent backup.

Alright! Re-enabled xCache for the main site. Everything is working as expected. Thanks everyone for your help!! Hopefully this might save someone else a few headaches if they are making a test environment and also have xCache turned on. Also, tools.php is your friend :)