I've a Midisport 2x2 "anniversary" that has never worked properly post Wn Vista. Under Win 7 it kind of worked but scrambled sysex and NRPNs. That's using either M-Audio's driver (necessary for multi-client operation) or the generic Windows MIDI one. The only driver that worked at all under Windows 8 was the M-Audio one for Windows 7, not the later driver Win7 release.
This is nothing to do with Sonar as I had the same problems with it in Sonar, MidiOx, Soundtower's Mopho editor and Live Lite.
As M-Audio have been passed from owner to owner over the last few years their driver support, both in terms of general quality and keeping up with new versions of Windows, has steadily got worse and worse.
I've given up an M-Audio. Too much stuff that they've abandoned driver support for or expect you to wait years for a driver that works with the latest Windows. I switched the M-Audio for a MOTO MIDI interface and all the MIDI problems went away.