I just started using VST in my compositions. I find that now and then notes go missing.
 
I just created a simple project that has two different VST instruments:
FMMF and PSYNII
 
Neither seems to play the second midi note.
 
I have a Toshiba with 16GB RAM etc so it is a powerful enough machine. 
 
Any ideas?

Missing notes may be caused by too small a MIDI playback buffer. If this is the SONAR LE based on X1 try increasing "Prepare Using nnn Millisecond Buffers" in Preferences > MIDI > Playback and Recording from 250 to 500 or 750

Awesome, changed it to 750, it worked. Now I'm cookin' again.