It looks like there may be problems with the default Mandrake 10.1 configuration and some USB serial  devices. But we have a solution....

The visor driver is loaded when what we really want is usbserial.

You can tell if this is the problem by looking at :

cat /proc/bus/usb/devices

The driver assigned to your device will be visor.

A simple fix is to add visor to the modprobe blacklist by editing /etc/hotplug/blacklist

You should then be able to issue the modprobe command

modprobe usbserial vendor=xxxx product=xxxx

as expected or update the modpobe.conf as usual

options usbserial vendor=xxxx product=xxxx