Try this:mmmkay; i'm on OS 3.0 NOT jailbroken and i'm getting that same 0xE800003D error. Since I'm not on a jailbreak I don't have the Cydia At&t logo so i'm stumped.
I don't want to upgrade to 3.1 b/c i don't want to lose tethering. Li'l help?
Works for me and I can confirm that the benm tethering hack still works afterwards. So I now have tethering and MMS on 3.01 using itunes 8.
Those who think aT&T tethering is working under 5.5 are probably wrong.
Try to use it.
If it does work for you...please mention if you hacked your phone beyond just installing a carrier file.
I looked up your problem in google. Seems like its a problem with your computer
http://forums.ilounge.com/showthread.php?t=215463
I could try reinstalling iTunes, and in that doesn't work. Reinstall your drivers for your usb 2.0.
OP - why is the first link a ipcc that is 33k in size and the alt link is 59k in size?
Added the IPCC to get MMS, Tethering, and Visual Voice Mail ALL working. Tested on my 3.0.1 32G 3GS and all are working perfectly. (Must be on 3.0 or 3.0.1)