I saw this mentioned one other place, I just don't remember where. Anyway, as I write this I am tethering with my Captivate using only the "PC Internet" option under Settings>Applications>USB Settings. I'm not running any other tethering program nor am I using the google codes .apk that's been floating around that is supposed to allow tethering on the Captivate. Tethering just works. At least for me.
Just thought I'd pass along the info.
Just thought I'd pass along the info.