If you cannot pinpoint what actually changed when it stopped working, I would suggest that you do a Windows System Restore to a point just before your MIDI stopped working.
Did you update any drivers etc? Or do you think it coincided with the install of Reason? [Have to ask if your copy of Reason was full retail or not? "Other" sources may well have dumped a virus on you or deleted a file during their "install" process.]
Hopefully going back to a time when it DID work, your MIDI system will be functional again ... it does seem more an OS based problem as it seems to affect many MIDI systems, rather than only one.
Have you done a full virus scan and also scanned with SpyBot Search and Destroy and/or Malwarebytes
http://www.safer-networking.org/
http://www.malwarebytes.org/products/
Hope this helps.
db