[Solved] AudioBox iTwo dropping out- audio engine stops. Please Help

I recently purchased a Presonis Audiobox itwo interface because my maudio fast track ultra  crapped out.  I am working on a project In Sonar Professional that has  35 synth instrument tracks, and had no problem playing them with the audiobox set to extra safe (highest latency). The project is 44.1K 24 bit.   I rendered the midi tracks to audio, then froze the synths and archived the instrument tracks.  So with the 35 audio tracks only , I am getting dropout- within a few seconds (audio engine stops).  I have to archive four of the audio tracks to get the project to play.  I had no problem playing 35 audio tracks with the Fast Track Ultra, but then I was using X3.
 
The only anti-virus I have is Windows Defender- but I don't see how that could be the cause if I was able to run 35 VST Instrument tracks. 
Could I have over-reached for the audiobox capabilities or is this more likely to be a computer issue or possible settings in Professional?  
Any advice would be greatly appreciated.
 
edit: added [Solved] to subject line - sc
 
 

scook
Since it is all audio it would suggest disk I/O buffering problem, see http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Troubleshooting.20.html
 

Thanks Skook I forgot all about that feature.  I will play with it and see what I get.