I believe it was the part about activating the accelerator. Something was screwy with it. I just turned it off and back on, then refreshed the board cache (in the CP), and now it seems to work when logged out.
Gremlins I tell ya!
[edit below]
When a visitor tries to visit:
http://www.catcherman.com/ubb/ultimatebb.php/ubb/forum/f/1 is when the screenshot above happens.
I can't figure out what's causing the problem.