Parallels just released release candidate 2 of version 2.5 of their x86 virtualization software and the last thing that was making me keep a Windows box around is finally working reliably.
I can now connect my Garmin GPSMap 60C to the virtualized Windows instance and successfully send and receive all data from it. No more USB conflicts, no more frustration.
And best of all, no more Windows box. I can finally shut it down for good. Good bye and good riddance!