I have the same problem in that the Polar UBS IR device cannot be "installed" on the XP Pro Parallels "machine". The message I get is "Unable to connect the USB device to your virtual machine.
The device cannot be connected now. Please try again later."
Here is my setup:
Mac mini running OSX 10.6.6, Build 10J567, 2.66 GHz Intel Core 2 Duo, 4 GB Ram
Parallels 6.0.11992, Revision 625164 (not using bootcamp)
Windows XP PRO, ver 2002 ,Service Pack 3
I downloaded the most recent XP drivers from Polar USA (as of Feb 17, 2011)
I have restarted the XP machine since the driver installation.
Since Parallels is a new installation for me this has never worked.
Any help would be appreciated