When I delete notes in PRV, they aren't there anymore, but I still hear them...
I have to go to event list and delete them ...weird!

I was unable to duplicate that here. Could be some explanation other than a SONAR bug. Perhaps a duplicate MIDI track? Do the notes continue to play with that track soloed?

Same as Dave, I cant duplicate it either.
Its very easy to delete a different tracks notes in the PRV. I've done it before.
However if your tracks are different colors that will give you a clear indication of the color of notes you are deleting in the PRV
 

Maybe there was a track way down the page duplicated...I'll ck

i'm having all kinds of trouble with the Tascam 20x20 having problems with the Windows Creator update...audio keeps stopping and I have to switch to another driver, then back to the Tascam ASIO to get it to play again...driving me crazy! 

Re-install the Tascam drivers

There was a known issue a while ago with 20x20 incompatibility. don't know if it was fixed or not, but the workaround was to set the format to 12-channel. 
 
There's an FAQ about using the 20x20 at 196 kHz that shows how to set the format to 12 channels. The important part is the 12-channel format, regardless of the sample rate.