Here are the cabs I've dowloaded to get this to work "to no avail":
Name Size
Calkulin's WM6.5 Tethering Fix 24.6K
Chainfire's Internet Connection Sharing ICS 174K
ICS and WModem Fix 84.7K
Mr.X and Mighty Mikes Tethering Tracking Hotfix (same as Calkulin's) 24.7K
RsBrowns69 TP2 Tethering Fix Mar 20 2010 (2 auto registry edits) 1.28K
One of these ought to work, as you all are having no problems.
I've also done all of Boo Boo's Reg Edits. Something's gotta give. After I flash the Sprint 6.5 ROM, I ought to be able to tether by using at least one of these options... I'm so frustrated.