With widows XP is not possible to open a console via serial port
with a switch catalyst 29xx or 35xx.
It is not a trouble with the switch because with windows 98 the
connection work fine, and is not a trouble with the config
because the same connection in Windows XP with a router 36xx
or 65xx work fine.
Ca you have a look if is a problem with the IOS of switches ?
Try using the SecureCRT® version 3.4.3 software from Vandyke software.
I been using this software for while and it is working great disregard which OS are you using.