Hey JT. I would suggest you try the suggestions here to find the solution to your stuck notes issue before you download the new Sonar demo. It is much more likely to be a system issue rather than software. Once you have your system ticking along, I think you will be very impressed with how far Sonar has come in the last 12 months.
 
I too have a couple of Macs that I use for various things but still use Sonar as my main DAW.
 
Welcome back!

Hey guys!
Wow, I love all the help I got here, including the great great great Craig Anderton!!!!
SO... I did go to my "preferences", set the MIDI playback buffer to as much as 2000ms, and also increased my Tascam's latency to higher than normal.
I do have 4 MIDI tracks, assigned to 4 VST instruments.
Here's exactly what I am getting - If I mute all but one track, when I hit spacebar to Stop, everything's cool. However, if I do unmute at least 1 of any other track, when I hit spacebar to Stop, that's when the stuck-notes occur!
My Question: When you hit spacebar to Stop, shouldn't an all-notes-off MIDI message be sent???? Why is any of the additional VSTs getting stuck??
And surely, I can simultaneously be able to play multiple MIDI-to-VST tracks, right????? I mean, that's the point of DAWs, right?
You all got me on a mission here, fix this bugger!!!!
Thank you all so much for the help, really appreciate the time and effort from you all to help lil ol' me....

....Another thing I tried: in the Audio Configuration settings/file, I did set the ExtraPluginBufs up to a value of "8". Didn't fix the problem, but am I at least barking up the right tree??

What synths? Any CC64 sustain controllers in the tracks? Try enabling Zero Controllers When Play Stops in Preferences. Disabling Always Stream Audio Through FX may also help.
 
And per my earlier post are the synths in FX bins or in the synth rack?
 
 

Is the Oxygen keyboard connecting directly to a motherboard USB port, or through a hub? Hubs are problematic, and a 1.1 USB device is a little scary. Also try disabling the surround audio i Device Manager, you almost certainly don't need it and it may be causing issues.
 
The "it works with other programs" may or may not be relevant. SONAR is tied very deeply into the Windows OS (which is one reason I am quite sure a Mac version will never exist). This has the advantage of being able to take advantage of Windows features, but the disadvantage of being very sensitive to the host environment.
 
Finally, Platinum did modify the MIDI engine so there's always an exact match between note on and note off events. IIRC this was about fixing some specific stuck note issue, which may apply to your situation. How about this: Set a system restore point, try the Platinum demo, and see if there problem goes away.
 

I have noticed one problem with my USB MIDI Controller keyboard [NEKTAR LX61], even if I connect it MB-USB port sometimes it get disconnected. Plug-out and plug-in solves the problem. Later I have noticed it happens when my power goes off and UPS comes in. Though the indicators on the keyboard never goes blank.
 
This cannot be any issue with SONAR.

I have "interesting USB issues" with both Mac and Windows. Still haven't figured out the exact reason why some things need to be powered on before booting, some need to be powered on after booting, some things lose their connections (even though I've disabled USB power management in Device Manager).
 
I'm basically resigned to computer and software sometimes behaving erratically, and this started back when I was using Z80s with CP/M and 8" floppy disks...  So I just do what I need to do, like unplug/re-plug, or re-boot, and carry on. Life in the modern world, and all that.

Just relating to the USB disconnect issue, I have this Reloop DJ controller thing that randomly stopped functioning. I would have to disconnect and reconnect it and reboot Traktor. So I never trusted it for a live situation, I tried all five USB ports on my laptop (2 are USB 3 and one is a high power USB 2 port) with no difference. For some reason I got the idea to try different USB cables. Even though the cable looks fine and works perfectly well on other devices, I might add. The THIRD cable completely solved my issues! It may have been the included cable, I don't remember. But apparently not all USB cables are created equal. Worth a try if you have a few cables lying around.

This doesn't seem directly related to the stuck notes issue. It almost seems like a midi loop to me.

Good morning, fellas....
Wow, again, thanks for all the help and posts.
@ Brundlefly - Yes, I do "insert" the VSTi's appropriately, not through the FX thing.
I will try to change the settings as some of you had suggested, as well as try different USB cables and ports (and no, it is not connected to a USB hub - I already know to avoid that.)
 
Thanks again, and I'll keep you folks posted....
Have a great day!

@ Brundlefly - 
I disabled Stream audio through FX, but I cannot find the setting for Zero controllers when play stops - where exactly is that setting??
 
Thanks!