Driver is signed, but Vista x64 thinks it isn't

Joined: Sep 21, 2009 Posts: 1

We've developed a driver that is designed to run under both 32- and 64-bit versions of Vista. We sign the drivers using the DDK signtool command, applying a VeriSign certificate we've purchased. The drivers load and run fine on our 32-bit systems but when we try to load the drivers on our 64 bit systems Windows complains that the driver is not signed. The sysinternals tool sigcheck though says that it is:

Code:

$ \\live.sysinternals.com\tools\sigcheck.exe -q -i -h -m -r mydriver.sys

Catalog: C:\Users\psteele\mydriver.sys
Signers:
MaxiScale, Inc.
VeriSign Class 3 Code Signing 2009-2 CA
Class 3 Public Primary Certification Authority
Signing date: 7:19 AM 9/21/2009
Strong Name: Unsigned
Publisher: MaxiScale, Inc.
Description: My Driver
Product: My Driver
Version: 1.1.0.305
File version: 1.1.0.305
MD5: c0aff971cb3ad93d6d58f8ecc4535cce
SHA1: 91074149c26e6c6821ce6575a3a570305f799875
SHA256: c4092f6176e19c47c688dfdaca66fbeb641c992dbcb036d22c4907d4315dd0bc

Additionally, if we view the Properties of the driver it clearly shows that it is digitally signed and everything is in order. However, there are various errors in the event logs related to this driver. This is reported in the Security logs:

Code integrity determined that the image hash of a file is not valid. The file could be corrupt due to unauthorized modification or the invalid hash could indicate a potential disk device error.

and we see this error in the System logs:

The MyDriver service failed to start because of the following error:
Windows cannot verify the digital signature for this file. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source.

What would cause Vista to think a driver isn't signed when it is when all indications are that it is?