Insmod segfault when loading custom module

I'm wondering if there is a better place for question of this nature, but:

I'm having major problems with a custom module on Fedora Core 3 systems,
and also Red Hat EL 4. When doing an insmod, I get a segfault, and the
syslog messages included below. A variant of the driver source code is
also attached to this message - this is a module containing only a
simplified version of the init code triggering the crash, which
reproduces the problem quite nicely.

Any ideas what is wrong?

Mar 16 17:37:25 hai kernel: Unable to handle kernel paging request at
virtual address 693e3660
Mar 16 17:37:25 hai kernel:  printing eip:
Mar 16 17:37:25 hai kernel: c01d9141
Mar 16 17:37:25 hai kernel: *pde = 00000000
Mar 16 17:37:25 hai kernel: Oops: 0000 [#1]
Mar 16 17:37:25 hai kernel: Modules linked in: itifg8tst loop nfsd
exportfs lp nfs lockd sunrpc video button battery ac md5 ipv6 parport_pc
parport via686a i2c_sensor i2c_core 3c59x mii floppy dm_snapshot dm_zero
dm_mirror ext3 jbd dm_mod aic7xxx sd_mod scsi_mod
Mar 16 17:37:25 hai kernel: CPU:    0
Mar 16 17:37:25 hai kernel: EIP:    0060:[<c01d9141>]    Not tainted VLI
Mar 16 17:37:25 hai kernel: EFLAGS: 00010217   (2.6.11.4-0.EL.toralf)
Mar 16 17:37:25 hai kernel: EIP is at pci_find_subsys+0xef/0x1a2
Mar 16 17:37:25 hai kernel: eax: 00000000   ebx: 693e363c   ecx:
ffffffff   edx: 693e363c
Mar 16 17:37:25 hai kernel: esi: ffffffff   edi: ce96df1c   ebp:
00000021   esp: ce96df78
Mar 16 17:37:25 hai kernel: ds: 007b   es: 007b   ss: 0068
Mar 16 17:37:25 hai kernel: Process insmod (pid: 6894,
threadinfo=ce96c000 task=d6c40f70)
Mar 16 17:37:25 hai kernel: Stack: ffffffff 00000000 0045f378 ce96c000
c01d91ff
ffffffff ce96df38 e0978053
Mar 16 17:37:25 hai kernel:        ffffffff ffffffff 00000000 00000000
e0912580
00000000 e0912580 c013687d
Mar 16 17:37:25 hai kernel:        0804a018 00000000 c0103281 0804a018
00000d96
0804a008 00000000 0045f378
Mar 16 17:37:25 hai kernel: Call Trace:
Mar 16 17:37:25 hai kernel:  [<c01d91ff>] pci_find_device+0xb/0xe
Mar 16 17:37:25 hai kernel:  [<e0978053>] iti_os_attach+0x53/0x60
[itifg8tst]
Mar 16 17:37:25 hai kernel:  [<c013687d>] sys_init_module+0x1dd/0x2b6
Mar 16 17:37:25 hai kernel:  [<c0103281>] sysenter_past_esp+0x52/0x75
Mar 16 17:37:25 hai kernel: Code: cf db 31 c0 c7 05 10 f6 35 c0 aa 00 00
00 74 04 8b 13 eb 4c 8b 15 e8 f2 35 c0 eb 44 81 fa e8 f2 35 c0 74 40 83
fd ff 89 d3 74
08 <0f> b7 42 24 39 e8 75 2b 83 ff ff 74 08 0f b7 43 26 39 f8 75 1e

#include <linux/version.h>	/* LINUX_VERSION_CODE */

#include <linux/pci.h>		/* pci specific stuff */

#ifdef MODULE
#include <linux/module.h>	/* init_/cleanup_ module */


MODULE_DESCRIPTION("CorecoImaging device driver test");
MODULE_AUTHOR("Matthias Stein");
#if LINUX_VERSION_CODE >= 0x02040a /* 2.4.10 */
MODULE_LICENSE("GPL");
#endif


#define ITI_LOG_STRING "itifg "

int
iti_printi (const char *fmt, ...)
{
  int retval;
  char string[80] = KERN_INFO ITI_LOG_STRING;
  long a, b, c, d;
  va_list argptr;

  strcat (string, fmt);
  va_start (argptr, fmt);
  a = va_arg (argptr, long);
  b = va_arg (argptr, long);
  c = va_arg (argptr, long);
  d = va_arg (argptr, long);
  retval = printk (string, 'I', a, b, c, d);
  va_end (argptr);
  
  return retval;
}

static int __exit
iti_os_detach (void)
{  
  return 0;
}

static __init int
iti_os_attach (void)
{
  struct pci_dev *the_dev;
  
  iti_printi("Scanning all devices...\n");
  
  the_dev=NULL;
  while((the_dev=pci_find_device(PCI_ANY_ID, PCI_ANY_ID, the_dev))) {
    iti_printi("Slot %s: Device %04hx:%04hx\n",
	       the_dev->slot_name, the_dev->vendor, the_dev->device);
  }
  
  
  return 0;
}
#endif /* MODULE */

module_init(iti_os_attach);
module_exit(iti_os_detach);