John,
I don't think the plus version will make any difference in this case as it is a matter of the receiver chip config that is most likely the issue. I am actually not using windows for a music computer anymore -- either my mac mini or a dedicated, single-board linux box, and the HRT works without issue on either.
Note, if you are using Win 7 or vista, check with Kevin about your firmware version. If the MS2 is new it will most likely have firmware 1.5 which works great with XP, linux and OSX, but seems to have problems with WASAPI under the newer windows operating systems, and you may have to roll back to firmware 1.4 if that is the case. 1.5 was a patch to correct some problems with playback of 24/88 files under OSX. There are utilities on the HRT web site that will tell you what firmware version you have, but check with HRT first as if you don't do the patch right you can mess things up.
HTH,
Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)