Switching to X2 - Stutter on first note

I just switched from X1 Producer to X2 Producer.  I am trying to import my X1 projects but I'm having a problem.  My X1 Producer was running in 32-bit mode and my X2 is running in 64-bit.  Some of my projects had frozen tracks, and when I imported them, I could not unfreeze the synths.  So I've been replacing the synths with 64-bit.  However, one problem I can't seem to whip is that one of my projects starts out with a piano solo.  The first note is a quarter note but on playback it stutters.  The rest of the track sounds fine, but that first note sounds like a 32nd note followed by a quarter note.  Any ideas what it might be?

MIDI buffer settings may indeed be the problem.

Another possibility is that the note that's not playing properly is on the first beast of bar one in the timeline?

If so it may be that Sonar's doing so much "behind the scenes" at that point that MIDI timing gets briefly out of sync. If the problem note is in bar one try shifting the entire project to leave a bar or two of silence (or more) at the beginning. 

It's been a rule of thumb in software sequencers ever since there were software sequencers that it's been a bad idea to put any MIDI notes or audio on beat one, bar one because it's asking for exactly the problem you have found. Some people recommend leaving one bar, others two, others recommend more. I often use 8, but that's so I can shove an intro in later if I want to :-)
It requires an amount of time, however short, for any DAW to check MIDI and audio sync plus handle the other stuff it sends at the start of a project - program/bank changes, controllers, MIDI Start, whatever. Asking for a note-on to be accurately sent on the first MIDI click of the project as well as all this stuff is a bit optimistic. 

If you've got away with it before, you've been lucky.

The PC in my sig is pretty powerful, but I wouldn't expect it to reliably start playing a project with a MIDI note on beat 1/bar 1. It might, if it's a very simple project, but once the data builds up it gets less and less likely.