Ohh... my....
[high]* 007 slaps self
[/high]
Here's what happened. When I instaleld 3.0, I clicked upgrade. Well, I thought the code edits that it told me were based on what was in my current code, and I ended up leaving Step 2 from 2.0 in my functions_showthread.php file, which obviously caused problems.
It's working fine now with 3.10. Sorry for all the trouble!
Awesome hack!