I have East West Quantum Leap Pianos on a track.  I use it a lot but in several songs I try to freeze the track to free up the s/w for other things.  Each every time, it cuts off sustain notes and other weird little hiccups making the function completely worthless.  It seems to work fine on smaller or shorter tracks, for example if I freeze an 8 bar phrase it works fine.  But a whole song forget it...
there seems to be an almost constant problem with Sonar cutting off sustain notes.  Sometimes I have to re record an entire track because I cannot resolve this issue.  I never had the issue prior to switching to platinum... 

Hi. If the tails of your MIDI clips get cut when freezing, try extending the clip before freezing.
If the MIDI track consists of several clips, try extending each clip, or bounce all clips to one and extend the end.
Best of luck.

+1 on extending the clips.  This is not just East West.  I always extend clips for sustained bass or piano notes at the end of tracks.  I do find it easier to bounce all the MIDI clips to one clip so you only have to drag out the end of one clip to fix everything.
 
Note that I find some soft synths are quirky when freezing.  For example, I love RealGuitar, but sometimes I have to freeze/unfreeze/refreeze a couple of times to get it to sound right.  Same thing with EZ Drummer.  Vienna and Play (East-West) seem to work fine.

Make sure you turn off "fast bounce" when you're freezing. That can cause bad bounces or freezes with a lot of synths...

konradh
+1 on extending the clips.  This is not just East West.  I always extend clips for sustained bass or piano notes at the end of tracks.

Right-click the Freeze button to get options, including "tail duration".

brundlefly
 
Right-click the Freeze button to get options, including "tail duration".

That I did not know. Thanks