These Yamaha USB drivers seems to get revised/updated every other month or so. I guess it is in response to all the many people who have had problems with the driver? I have read on another forum that version 2.1.4 is considered the most stable. It is the one that works for me. It is interesting to note that Yamaha labelled version 2.1.5 as the Windows XP SP2 compatible version. I run Service Pack 2 on my computers and the prior version (2.1.4) works just fine.

I do not have any other MIDI USB drivers installed except for a MidiSport 2x2 driver.

Tom G.