The Issue I was having with this with itunes 8, was that i kept getting SPAMMED with errors from applemobiledevicehelper.exe that it had stopped working as soon as i plugged in my Iphone 3G to the USB and itunes started up and syncing began.
Solution: Went to Control Panel and found the Apple mobile device helper installation under Control Panel ===> Programs and Features and right clicked and pressed repair....NOW it diddnt work the first time, but i did not give up
and I went crazy and tried it again
..hehe and WHABLAM problem solved!!!
My OS is Windows Vista Ultimate 64bit.
Regards
Roger Zimmer
Simplefying life is devine!!!