isr handler kernel problem

I'm working on a kernel module interrupt handler. I stripped the problem
down with a parallel port handler and get the following result:

initializing module
Badness in enable_irq at kernel/irq/manage.c:109
 [<c014e864>] enable_irq+0x84/0xf0
 [<f938b05a>] initialize_module+0x5a/0x81 [parint_mod]
 [<c0143a8c>] sys_init_module+0xcc/0x1e0
 [<c0163878>] sys_munmap+0x48/0x70
 [<c01042cb>] sysenter_past_esp+0x54/0x79
cleaning up module

this is the stripped down module:
irqreturn_t interrupt_handler(int irq, void *dev_id, struct pt_regs *regs){
        interruptcount++;
        printk("######INT######\n");
        return IRQ_HANDLED;
}

static int __init initialize_module(void){
        int ret;

        printk("initializing module\n");
        ret = request_irq(PAR_PORT_INT, interrupt_handler, SA_INTERRUPT,
"parallelport",
                        NULL);
        if (ret != 0) {
                printk("init of irq handler ret: %d\n", ret);
                return ret;
        }

        enable_irq(PAR_PORT_INT);
        outb_p(0x10, BASEPORT+2);//set interrupt mode
        outb_p(0, BASEPORT);//force interrupt
        outb_p(255, BASEPORT);
        outb_p(0, BASEPORT);

        return 0;
}

The module loads perfect. In init_module I just toggle the interrupt line
and /proc/interrupts reflects the incrementing interrupts. However the
handler just crashes.
The system is an updated suse 10.0 kernel (2.6.13-15.11). Installed on a
suse 9.2 system it runs perfectly, so it's a real kernel problem.
Anybody familiar with this kernel problem?
taco