Yum, HAT! *sigh*
Well, Rob, I am glad that the test install works.
Next up... very carefully, on the main (broken) board, delete the UBB scripts (but not the vars_ files), the entire Modules directory, and the noncgi/Templates directory, then replace them all with stock copies from the zip.
The delete step is very important.
Does that bring the main board back to life?