** Updated 12/2/2012 **
Just upgraded to iTunes 11.0.0.163 and the issue has not improved at all. I reenabled my Wi-Fi sync and it seemed to take a while longer before the AppleMobileDeviceHelper.exe started consuming CPU like crazy (about 5-6 hours) but consume it did. Also the iPhone and iPad completely don’t see the server so Wi-Fi sync is still broken. I’ve disabled that mode of syncing again. I suppose it will have to be an iTunes 12 fix?
** End Update **
So, it turns out that disabling sync over Wi-Fi eliminates the high CPU consumption issues with both the AppleMobileDeviceHelper.exe and ATH.exe
This is relatively painless to do since the Wi-Fi sync stopped working with the 10.7 iTunes update on the Windows 7 (64 bit) release anyway.
I’ll leave this disabled until the next iTunes update. It’s a shame because the Wi-Fi sync is a pretty slick feature.
To disable, just plug your iDevice into your computer and, in iTunes on the Summary page, uncheck the “Sync with this computer over Wi-Fi” checkbox and click apply
This solution worked perfectly for me. I have Windows XP. Follow these steps: 1) uninstall the latest release of Itunes. 2)Reinstall Itunes version 10. 3) Go to the Apple support website and search for Recreate Itunes Library instructions. It will tell you to drag the Itunes.xml file to your desktop. 4) Drag the Itunes.itl file to the recycle bin. 5) Now Open the newly installed Itunes. Select File, Library, Import Playlist and choose the .xml file you placed on your desktop. It will import the list and then synchronize all of the files on your Ipod. No problem with high cpu usage until Apple fixes version 11.
This solution gets around the problem of not being able to go to a previous version because the new release of Itunes prohibits reading the older files.