COM port redirection issue

I've got 2 ubuntu 10.04 ltsp based thin clients setup connecting to
the same 2003 terminal server with com port redirection.  The first
one I setup works fine, but the 2nd is having some issues.

First is using "-r comport:COM2=/dev/ttyS1", 2nd is using "-r
comport:COM4=/dev/ttyS1"
The main symptom is that the when the application using the com port
on the 2nd tries to close the port, the entire RDP session hangs for
about 20 seconds.  Occasionally opening the port again will fail, and
merely disconnecting and reconnecting the rdp session will allow it
again.

is there some way to get rdesktop to complain about what's going on,
maybe log to a file, so i can pinpoint what to fix?

some history that may help:  the original system is a P200 running
windows 95.  I have tried to replace this system with newer computers
locally running 95, 98, 2000, and xp pro and hardwares p2-400, p3-800,
P4 2.6Ghz, and AMD64 3800+ , and all of them fail in similar ways,
which is transfer errors though I do not see the hangs like with
rdesktop.  The older P200 does not fail on transfer errors using the
same software settings and cables.  I'm only using 9600baud, so the
slow PC speed really should not have any effect at all.  The system
that works has also had a history of transfer errors before using the
thin client, but since moving it to ltsp/rdesktop, it has had no
transfer issues at all.

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