After updating to 2.2 my computer would no longer charge my phone. It said it was charging but the battery would actually drain itself. This is because the computer no longer recognized the phone and did not change the USB output from 100mA to 500mA.
To fix this:
With your phone unplugged from your computer.
On your computer go to:
Start / Motorola / Motorola Driver Installer.exe
Select CLEAN only and hit Start.
Now go to
USB and PC Charging Drivers - Motorola, Inc. USA
download and install the new drivers.
Plug in your phone and enjoy.