On the song I started mixing in X2 and now continuing in X3 (producer 64 bit), I am having consistent issues when I select all tracks, select a range, copy, then paste at a later location.  What happens is that some tracks, guitar for example (not every one, just one or more) have takes pasted in the wrong locations. I set paste to "slide things"
 
Now, just to avoid the thought that I have never done this before, i have done this many, many times in X2. So it is not technique.
 
Note that so far at least, the problem tracks have multiple takes on them.
 
I experimented and same results in both comping mode and sound on sound mode.Also it doesn't make a difference copy and paste or cut and paste.
 
I did find a work around. Well.. at first I thought I'd just open it in X2, copy and paste. No joy there, X2 warns you that you are going to loose things when you save.
 
And so what I did is used Project > insert time measures, added the number of bars needed, then pasted over the blank area. That worked perfectly.
 
 

I have a similar issue...I select a region, copy it and move to the location where I want it pasted, hit the paste command and ... gone, where did it go??? I finally find it in a place that it was never intended for or wanted - 15 or so measures ahead and several tracks lower. And...it does it EVERY time. So I figure, since it didn't do it before, that I had inadvertently hit some keystroke that turned something on or off. Mine is a big project that I have worked on for 2 years and now it hates me.
 

Could you have accidentally pressed the 0 key?

I haven't run into the original issue - yet anyway. For funboy, sorry if this is missing the point but I sometimes forget to make sure the  now time marked is set to the location I want and I have the intended destination track selected. So if copy from tracks 1 -5, but happen to have track 2 selected when I paste, everything is one track down.
 
Might not be your issue, but maybe will help someone if it isn't

Use Paste > Special and set the track number of the highest numbered track there

Yes, copy and paste got real dodgy lately... I think before X3.. that is, one can have a track selected, the now time set, select some MIDI region, do a copy (CNTL-C), move the now time in the same track and hit paste (CNTL V) and NOTHING.  
 
But, I have learned that the NOTHING pasted isn't correct.  It pasted the MIDI notes somewhere but not where I thought... so a quick CNTL Z to undo the paste and start all over only this time I make sure before I select the region to copy, I make sure that it is the ONLY TRACK selected in TRACK view and the above process works as it should.  The odd thing is though that the TRACK was already selected the first time... for some reason, the second time is the charm.
 
Appears to be some type of bug to me and tied to MEMORY LEAK of editing and UN DO history.. which gets cleared up when one SAVES the project.  The MEMORY LEAK symptom is that the transports become real sluggish.. do a save and the transport functions become snappy again.
 
So, you are not crazy, the bakers should take a look at the editing functions of MIDI data.
 
Jim

Jim, I'm guessing your issue with sluggishness after doing a lot of MIDI editing (especially if it involves splitting clips) is due to having Non-destructive MIDI Editing enabled. This creates lots of hidden MIDI data (by making slip-edited copies of entire clips) that can cause large file sizes and potentially RAM/performance issues due to the size of the Undo stack and the number of events to be managed. Unless you have a reason for keeping this option enabled, I recommend you disable it.
 
I personally find that Non-destructive MIDI Editing causes very un-intuitive (even destructive) results when splitting, and usually have it off, but there are a handful of situations in which having it off gives unexpected/undesirable results.
 
Regarding Copy-Paste functionality, I didn't use X2 a lot because I wasn't making a lot of music last year so I can't comment on issues it may have had in that area. I've not encountered any problems in that area with X3, except the inability to paste to a specific lane or drag a partial MIDI selection directly to another lane, which I see more as missing features than defects.

I use Ctrl Z frequently when I copy and paste into the wrong spot.  It's easy to forget to select the right spot when you cut and paste in a hurry with Ctrl C and Ctrl V!

I was working on a project for a buddy that wanted backing tracks for an old country song. I use Band in a Box / Real Band to create the tracks then I import everything into Sonar to edit etc. He decided he wanted an additional Instrumental section so I figured no problem, I'll just select the first instrumental section and do a cut and paste. I selected about 8 tracks and tried to paste it where he wanted hoping that it would place it and bump everything down for the finish. It brought some tracks and not others and just overlaid on top of the last part of the song. I tried numerous times. I ended up loosing data and had to start over from scratch. This should be a simple task. I use Producer X3

There used to be a bug where ctrl+a would sometimes not select everything.
 
I don't know if it's still a bug. I haven't noticed it in X3e. Usually when using ctrl+a you can ctrl+click extra items that didn't get selected with ctrl+a.
 
I usually bump into this myself when I'm wiping out an initial test record before I really start the session. I often set up and start the recording as the band gets ready and tunes up. Then, I ctrl+a then w for rtz and delete before starting the session. The bug shows when a couple of clips are left. It always works to hit the key strokes again to delete all.
 
I don't know if this helps.