Tracks done on my 1640 barely work on the Blackbird.  I get stopped no matter what setting the Latency or how few tracks or ASIO or WDM...it doesn't matter.  Has anyone had this problem?   Everything being the same, why don't 1640 files work with the Blackbird?  Anything new recorded on the Blackbird works fine.  
thanks,
Wadrum

What is happening exactly?  I know you've tried changing latencies, but make sure all of the other settings match those of the newer projects.