NT 4.0/Delphi Serial Problem

  We have created an application that talks to a video switcher via
com1 on a Win 95 machine using Delphi 2.0, it works great.  We would
need to move it to an NT4.0 machine.  It initializes fine but hangs
when we  try to transmit.  We have tried another NT system with the
same  result.

     Thanks for any info