MSD issues!?

I purchased a MP MSD unit and installed in my 73 Dart that was working fine with a MP distributor and a MP chrome ECU. Car starts and runs fine for a while.

After a few runs down the track, car fails to start (basically acts like a not spark condition). So I switch wiring back to the MP chrome box and it starts right up. This has happened to me twice, since I tried running a ground from engine to the body and tried unit again.

I called the place who sold me the MSD unit and they say my issue is probably related to something not being grounded properly.

Has anyone out there had an MSD that would loose ability to fire once it gets hot?

Has anyone had a similar condition that was a grounding issue??