I've tried more than a dozen times to do a simple copy/paste, and it simply doesn't work.  I highlight and specify a range, Copy, and then GoTo the bar I want to paste to (like I've done a BILLION times before) and Paste isn't even listed as an option.  I've shutdown, rebooted, and still won't work.

probably don't have the right thing selected.
 
Like on the left side you can use a drop down to select clips or envelopes or other things.
 
Make sure you are selecting what you want.
 
When you get better, you can shift click on the stuff you want to set the focus. Then copy paste works fine.

Click the track, clip and highlight it then select CTL+C
 
Click the track number were you want the clip, audio, or file to go, move the now time to where you want the pasting to start and perform, CTL+ V
 
Done

Had similar issues today. I was trying to do a simply copy and past audio. Did all the right things, select a region in the track, Control C, then select where the copy should go, in the same track. Hit Control V and WTF.
A new track is ADDED and selection pasted randomly along it!!!
Weird !!!
Tried allsorts of ways to copy/paste, but each time a new track was added.
In the end I had to back out and close Sonar.
 
On reopening all was fine. Copy/paste worked normally.
Go figure.

Copy and paste works but you have to be careful to choose the correct source and destination. The most common issue occurs when you select the track you want to copy, but a different track has the focus. The paste will occur at the track with the focus, not the track you selected. The reason for this is so you can copy material from one track to a different track, i.e., not paste over the material in the same track.