One way to totally lock up the I/O ports is to do the following:

1) Set XON/XOFF flow control on the port (stty says " ixon")
2) Connect
3) Get the remote end of the link to send a ^S (XOFF).

BOOM!  That port (and any process that has it open) is hung until you
reboot, unless the remote end sends a ^Q (XON).

I do not consider this to be a bug in the com driver, but that doesn't
keep it from being annoying.
-- 
Mike Long <mike.long@analog.com>       PGP 2.6.2 public key signature:
VLSI Design Engineer                  CCBF225E7D3F7ECB2C8F7ABB15D9BE7B
Analog Devices, CPD Division
Norwood, MA 02062 USA                assert(*this!=opinionof(Analog));