Melodyne clips freeze Sonar when saving

Try bouncing your Melodyned clips to track once you're happy with your edits.  To be on the safe side, clone a copy of the original track and hide it with track manager.  You should be able to save after this.

I have not used Melodyne in Platinum (yet), but in X3 Melodyne changes were actually saved within the cwp itself (if still active). There may be something going on with that part of things. Two things I try never to leave active are Region FX and AudioSnap adjustments.
 
With Melodyne, I have found it best to do surgical edits and bounce when finished (you can always edit material again if desired). Any time you bounce, SONAR replaces the wav file beneath a clip but does not delete the original (that will remain in your project/audio folder unless you manually delete it).