USB to RS232 Serial Converter Problem

Hello,

I have a problem using USB to Serial converters with
Windows XP. My application works with native serial ports
on all versions of Windows (95 through to XP), and with
USB converters on all Windows platforms EXCEPT XP.

I have tried several different converters, installed the
latest drivers, and even tried different PCs. The problem
definately only appears with Windows XP (particularly on
laptops), with all makes of converter and my bespoke
application written a while ago in MFC (old I know, but
then that's the point of the converter isn't it?).

Has anyone had similar problems, and is there a known fix
for either Windows XP configuration, the converter or the
manner in which the application uses the serial port?

Many thanks to anyone who can help with this!

Gary