[gxnext]

lol well I don't know if im smarter than you or not, but ill tell you what works for me... im using rom 2.17, really you don't need to do anything but OPEN your pocket internet explorer (or anything to start the evdo connection) then start Internet Sharing. but I used the reg edit [HKEY_LOCAL_MACHINE\Comm\InternetSharing to delete
"Extension"="rilphone.dll" so it won't show that error... but i still need to open IE on this rom ver to get it to stay connected for some reason.. but with previous rom's it would just work without having to open ie after the reg edit..... but really im not sure if this is any help to you. but in my experience the trick is just to open IE then try IS.... and im sure you already know to make sure sprint pcs is selected under "network connection" b4 you connect with IS. (yay i just realized im a senior member now... finally lol currently we have the same amount of post what are the odds, congrats to u as well)
edit: this is my experience with vista and xp with the latest active sync and drivers installed. p.s. I don't think im smarter, I think your situation is unique and the problem could be more computer oriented...