I do this all the time. My life depends on it!
 
There's a stubborn instrument track that won't copy & paste. I try copying, then pasting, and nothing happens.
 
I've been using X2 a lot lately, since I've had some extra time, and composing music is my passion. My wife worries about me as I throw fits due to the myriad of bugs in X2. This one is especially annoying. Maybe my problem is that I'm in the wrong genre (classical).
 
Have a nice day!

Try empting out the Pic Cache folder..

Have you tried edit > paste special just to make sure you're pasting into the correct track?

I'd be 100% confident that after you "failed" paste, the undo button would read "undo paste" so the data has gone somewhere, just not where you think

I have found that all Sonar products are a bit testy in how they perform a paste. Nothing else I work in pastes like Sonar does. I have to be very precise and make sure I select the track I'm pasting to TWO times or it will paste somewhere else. When pasting multiple tracks, always have the first track selected that it's pasting to or you'll end up with a mess.

For example, I just pasted 8 back up vocal tracks later on in a song. When I do this, I of course select all the tracks that I'll be copying, copy them, and when I paste, if I do not un-select the tracks, I get pastes all over the place that are not correct. So after the copy function, I just select the first track in the series that will be pasted and all the others follow suit along with it. But I MUST select/hi-lite that first track of the paste or I'm doomed.

-Danny