Altima stalls when warmed up...can't find cause! Please help!

We have a 97 Altima w manual trans. It stalls when it get warmed up. Lift the hood and after half an hour or more will start and drive for a while. It has a new distributor and coil. Fuel pressure checks good when it won't run. No spark from coil when it acts up. Hoping its not the ECM... BTW it did act up the morning after one of these episodes when the engine was not hot! go figure... Any ideas? Thanks, Tim