Using my Korg Triton via Roland's UM-3G into a Windows 7 computer.  I have a certain way of powering things up because (on occasion) the Keyboard does not talk with the Computer/Sonar X3.
 
Recorded 2 nights ago.  All good.  Last night, Sonar X3 could not find the UM-3G, so I got the whole "continue without MIDI" dialog box.  Reboot.  No luck. 
 
Check Windows (Win 7 Home Professional) - it says the UM-3G driver is fine.
 
Double checked connections. 
 
Powered all stuff down [again] and executed the process per normal.  No luck.  Crap crap crap.
 
So, I've got some more testing to do this eve....
 
Hoping someone can point me to [free] Windows-based MIDI signal testing software.  I gotta figure out where the issue lies.  I saw midiox but am wondering if there is something a bit more modern out there. 
 
Many Thanks, music Bros/Broettes

I thought the UM-3G had a display of MIDI activity, if so, check you have a signal going in / out and that it leaves via the USB (also that the sliders are correct on the UM-3G!). Then check preferences in the Sonar program to verify the Korg has control (if that is your set-up), check MIDI info in DEVICES (MIDI menu). Sounds like an update has reassigned something and all it needs is resetting (BTW check if a lead has failed as well). Best of luck an' hope this helps.

MIDI-OX is great for testing your MIDI devices: http://midiox.com/
 
As long as you select your UM-3G's MIDI inputs and outputs, you should be able to monitor any MIDI activity from your keyboard.

Will add your items to my test list! Thanks.  My machine is an offline machine so No updates. 
I will check those UM-3G sliders though.  In case something bumped!
 
Don't know about UM-3G MIDI activity display....will check.
 
Stand Alone VSTs (IRSI/Kontakt) receive no signal either. So something outside of Sonar, I'm guessing!
 
Anyway....still hoping to find some MIDI troubleshooting software, also.
 
Cheers.
 

Joe Connor [Cakewalk]
MIDI-OX is great for testing your MIDI devices: http://midiox.com/

MIDI-OX it is!

When something crazy happens and I can't figure out how to fix it, I just restore the computer to a date just before it went wacky
Works 9 times out of 10 and saves a lot of time. Just a suggestion