Sync doesn't work since I fooled with COM ports

Yesterday I dinked around with COM port settings (Vista 64-bit) while
struggling to install a stubborn driver that wanted to assign itself a COM
port. Today I can't sync my phone. When I plug it in, I hear the beep that I
expect, and see the hourglass as WMDM and Sync Center try to connect. Then
they give up and simply report "Disconnected". No error.

Is there something related to COM ports that I need to check or fix? And if
not, what should I uninstall/reinstall to repair whatever setting I damaged?

Thank you!

-Doug