[plug] Debian serial port - gone missing

[Mark]

Hi all

I have a  Think Pad 760ED with  a  Debian Woody installed which has
been running quite sweetly till now.

The only external serial port on ttys0 seems to have gone ...?

When I run seyon to test it I get.

 >>Error: : Inappropriate ioctl for device.
modem '/dev/ttys0' is unavailable

Any ideas for what could be going on here.
The only changes I have made have been to config files for a wireless 
network
card.

I have eliminated hardware as a cause.

Mark