Application using serial port 'freezes' after a while in XP

I'm developing an application using Delphi and serial port
communication. My application works perfectly on Win 98
and Win 2000.

On Win XP the serial port communication 'freezes' after a
minute or so... It helps to either restert application or
to close->open comport inside application to get up and
running again (for another minute...)

When this error occurs the comport 'dies' in both receive
and transmit directions. It seems that if my application
is forced to not transmit anything the comport (receiver)
will work fine...

Anyone experiencing similar or any ideas??