Make sure you are using a USB 2.0 port instead of a 3.0 port.  A lot of devices will not work with 3.0 ports. 
 

Windows has this dumb issue where it can't recognize more than ten midi devices. It can lead to all sorts of nastiness like what you're describing. Because of another Windows stupidity, a new midi device is created everytime you put the same device into another port (and possibly your "extender"), so it's pretty easy to run into this limit. I have to manually manage my midi devices a lot.

You could try downloading and installing any Korg midi driver (e.g. the Kronos one) from their support site. It comes with a midi driver removal utility that lets you completely remove old or corrupt Windows midi drivers. You need to uncheck a box when you run the utility to allow it to uninstall non-Korg drivers. I would recommend removing all of them and installing the UM1 and MidiSport fresh. I don't know for sure that this is at the root of your issue but it was definitely a pain for me until I figured it out.

'Preciate it, folks! Searching Kronos in the Start menu, shortcuts appear for KORGUM64 and KORGUMDN. Does that mean I already have it? Searching midi driver, a "Configure Korg USB MIDI Driver" choice appears. Clicking it, a little "Korg USB MIDI Driver" box appears, with options for only "Advanced: suppress device number in the port name of the first device" (unchecked box) and "MIDI In" (Both, 32bit only, 64bit only -- default of "Both" was in effect). Trying a search for MIDI devices and drivers nothing very useful comes up, mostly factory-looking. All four of my USBs are 3.0.
    Is there a way to just get into the puter and delete redundant (or all) MIDI drivers and then do a fresh install of the big two as Sanderxpander says?
    I had a great breakthrough on Sunday -- finally had the wits to set all I/O options correctly and was able to sequence on two instruments simultaneously, changing sounds freely. Had struggled with it many times before and suspect it was simply being able to cry on your shoulders that finally got me over.
   I don't assume anybody's interested in my ongoing saga but have just stashed the full update here since I can paste the whole shebang and will always know where to find it: (poormehelpme period blog spot period you know what).
Next stop -- how do I get my Sonar tracks playing through sounds built into Sonar's internal synths? No doubt it will also be simplicity personified, but all efforts at cracking the code have failed thus far.
 
 

what is the length of you midi cable extension?

Doktor Avalanche
Did you click on the link for updated drivers and firmware?

 

BachFugue
There was no link for updated drivers and firmware.

 
#5
 
 

"Next stop -- how do I get my Sonar tracks playing through sounds built into Sonar's internal synths?"
 
At the top click Insert>Soft Synths, select the synth you want to use.
A dialog box will appear with some options for you to select.
Since you already have MIDI tracks, uncheck 'Create MIDI Source Track'.
Once the synth is ready, just change the outputs of your MIDI tracks to the synth you just inserted. 
Some synths are multi-timbral and can have up to 16 MIDI tracks feeding them; others are not and can only send 1 MIDI track to them at a time.
Careful with the output levels of your synths, especially synthesizer synths (); some are very loud and can red-line your interface. Out of habit, I always reduce the synth output level before I hit play.

rabeach
what is the length of you midi cable extension?

About six feet. 
 
Glad you've mentioned this. I dream of positioning the Privia about 40 feet away at the other end of the church and having Sonar play it antiphonally from the front. Figuring it would need a connection at least 60 feet long running around under and above floors. Is there a limit -- or a delay? 
 
http://www.amazon.com/Sabrent-Meters-Active-Extension-Repeater/dp/B007VQNYSG/ref=sr_1_1?ie=UTF8&qid=1432130191&sr=8-1&keywords=usb+extension+cable+100+ft

57Gregy
At the top click Insert>Soft Synths, select the synth you want to use.
A dialog box will appear with some options for you to select.
Since you already have MIDI tracks, uncheck 'Create MIDI Source Track'.
Once the synth is ready, just change the outputs of your MIDI tracks to the synth you just inserted. 
Some synths are multi-timbral and can have up to 16 MIDI tracks feeding them; others are not and can only send 1 MIDI track to them at a time.
Careful with the output levels of your synths, especially synthesizer synths (); some are very loud and can red-line your interface. Out of habit, I always reduce the synth output level before I hit play.

Trying this with TTS-1 brings a most solid gray window with the track title at the top, and beneath it shortcuts for "Insert soft synths and ReWire devices," etc. and a long thin blue space containing the synth name, "no preset", forward and back arrows, and a blank line starting with a squarish letter C (or extremely bold left-bracket).
 
Checking the track for the piece I'd opened (about a week old), the output was already set for the synth, but playing the track I don't hear anything. Haven't seen anywhere to select a sound, so I must have missed something big.
 
Trying it with the Roland GrooveSynth I managed to bring up a window for it in addition to the above (which now has a blue bar for the GrooveSynth below the TTS-1 one) and selected a sound -- "real strings" -- but still no sound, regardless of how I set the track's output. Synth's level is set at 105 -- is that its volume level?
 
Computer sound still working normally. You mentioned the interface -- assume you mean the UM1 just in case it was still plugged in? It's not needed for this, right? 
 
Remembering the other controls above the onscreen volume slider I set them for "Ch 1:Roland...", "8192 bank" and "PizzicatoStr" as no Real Strings was among the choices -- still nothing. Trying the Assign Instruments box, the Output/Channel box in it is empty. All the due diligence I can think of!

Bowing out of this thread as I'm just talking to myself.

Doktor Avalanche
Bowing out of this thread as I'm just talking to myself.

Oops -- did I miss something you said?