Class coinstaller dll not signed problem

Hi,

I'm trying to create a system that can be used to control Plug and Play
installations. It should enable me to define which devices are allowed
to be installed by the logged in user and which drivers should be used
for the device. I'm doing this through a class coinstaller. It's not
intended for any specific device or device class. I want it to be used
by every device class on the system.
Everything is working quite properly, except that for every device in a
class that uses my coinstaller the "New Hardware Wizard" pops up. I
mean every installation, even with signed drivers and "standard windows
drivers". When i disable my coinstaller, the devices install fine with
the server side install (no wizard), but with the coinstaller enabled,
it always switches to the client side install. By now i've disabled all
the actual functionality in the coinstaller; it always returns
NO_ERROR, so it shouldn't be anything that the coinstaller does. In the
setupapi.log i found this:

#E358 An unsigned or incorrectly signed file
"C:\WINDOWS\System32\spdrcls.dll" for driver "iPod mini" blocked
(server install). Error 0x800b0100: No signature was present in the
subject.
#E161 Processing of call to class installer failed. Error 0x800b0100:
No signature was present in the subject.

It seems that the spdrcls.dll, my class coinstaller dll, is not signed.
I didn't sign it, so that is correct. Is there any way to get this
signed, or to get windows to ignore this? I've looked into the driver
signing info, but that doesn't really seem to apply here.

Any help would be greatly appreciated!!!

thanks

Krijn

FYI: Complete setupapi.log:

[2006/02/22 13:11:35 680.3 Driver Install]
#-019 Searching for hardware ID(s):
usb\vid_05ac&pid_1202&rev_0001,usb\vid_05ac&pid_1202
#-018 Searching for compatible ID(s):
usb\class_08&subclass_06&prot_50,usb\class_08&subclass_06,usb\class_08
#-198 Command line processed: C:\WINDOWS\system32\services.exe
#I022 Found "USB\Class_08&SubClass_06&Prot_50" in
C:\WINDOWS\inf\usbstor.inf; Device: "USB Mass Storage Device"; Driver:
"USB Mass Storage Device"; Provider: "Microsoft"; Mfg: "Compatible USB
storage device"; Section name: "USBSTOR_BULK".
#I023 Actual install section: [USBSTOR_BULK.NT]. Rank: 0x00002000.
Effective driver date: 07/01/2001.
#-148 Loading coinstaller modules for "iPod mini".
#E358 An unsigned or incorrectly signed file
"C:\WINDOWS\System32\spdrcls.dll" for driver "iPod mini" blocked
(server install). Error 0x800b0100: No signature was present in the
subject.
#E161 Processing of call to class installer failed. Error 0x800b0100:
No signature was present in the subject.