Try reinstalling Apple Mobile Device Service.

http://support.apple.com/kb/ht1747

I might suggest restarting after step 12 if that doesn't work. Maybe the kext can load without a restart but it's worth a shot.

Also, any reason you stopped at 10.6.1? Just curious, something you have that won't work past that?

Edit - Check out the Additional Information link at the bottom of the support page too.