ADSL Modem Installation problem

When installing a Sagem 800 modem on an ADSL service under Win XP Pro the service is accessible after first install but after a reboot or change to a new user a stop message is displayed as follows when you try to access the service again.
Error stop message :driver_irql_not_less_or_equal.
I understand this message relates to an interupt request but how can it be resolved?, could it be faulty hardware? or is it a corrupt driver? What part is the O/s playing in this if anything?