MIDI dropout in X2 but not in Sonar 7

I have a project that won't playback in X2 without some of the MIDI dropping out. Dropout occurs on almost all midi tracks, but not all at the same time. In some cases a whole bar is silent. Other times only one note of a chord is sounded. The one softsynth that is not dropping out is Battery 3, but it's worse because instead some drum beats are playing late.
 
Altering the audio settings doesn't make the slightest difference. High CPU activity is not indicated. I'm wondering if maybe it's a particular plugin effect that's causing the problem.  It's a big and complex project, which makes the problem hard to pin down.
 
The project was originally developed in Sonar 7, so I tried opening it in Sonar 7. It plays back perfectly there with no hint of any dropout. I now intend to work with it in S7 for a while and do some bouncing to audio before returning to X2. 

scook
The first thing to check when MIDI notes are dropping is the "Prepare Using nnn Millisecond Buffers" in Preferences > MIDI > Playback and Recording. The default setting was reduced in the X series from 500 to 250. Try setting the value to 500 or 750.

Thanks for the quick response.
 
I have never altered that setting before. It was set at 500 and I have now changed it to 1000. This looks promising. The project seems to playback ok now.
 
Buffer setting in Sonar 7 is 500 though. Why does X2 need higher?

scook
Generally newer software take more resources than older software. I do not know if this is the case here. SONAR is a complex application with so many changes in the application and the supporting libraries since version 7 it is reasonable to expect some fine tuning between different versions of the application on the same host.

That's generally true.  But, if I were a music software programmer, the efficiency of MIDI playback is not something that I would want to compromise for the sake of adding other features.

The vast majority of systems are happy at 500ms. X1 actually introduced a lower default of 250 that was too low for many systems, including mine. It's not clear what factors contribute to buffering problems that different systems exhibit, but raw system horsepower does not seem to be as much of a factor as what synths the project uses and other project-specific factors.
 
Also, I've found that there tends to be a "magic number" where problems suddenly disappear completely, and you may find that 550ms will do the trick. For me, the magic number is just barely over 250 for most projects, but 500 has always worked perfectly, and there didn't seem to be any particular value in running a smaller buffer so I've stuck with that.