I've been trying to fix my WM6 Professional mobile phone as it wouldn't sync with Windows Mobile Device Center.
I kept getting "ActiveSync encountered a problem on the desktop." with the error code 0x86000107.
I tried everything, a device hard reset, uninstalling and reinstalling Windows Mobile Device Center, Turn off all device security with Visual Studio, etc.
Then just before i was about to give up i turned off the USB to PC "advanced network functionality" and it started working again

As i couldn't find much information regarding the error code i'm posting my solution here.
Start --> Settings --> Connections --> USB to PC --> untick "Enable advanced network functionaility"
If anyone has a better solution let me know.