Are you using the newest version of the driver from Creative Labs? Do you have this issue immediately? Have you attempted to update Windows?
I did not check, but CL usually has Beta and release drivers. With 64-bit systems, I usually used the Beta drivers and only released drivers for 32-bit. My X-Fi Fatality has not had any issues for awhile, even though it is slightly different then Platinum.
BV EDIT: I do not have that particular file on my system, so it could be "missing" in your situation or that Vista is getting mad that they are Beta drivers and unsigned. Are you using the ones released June 26 (not Beta either)? I have not updated to that particular one, myself, and I do not see them as signed, just "release".
BV EDIT #2: I just looked closer and it looks as though the released and Beta drivers have the same version number, but the Beta is only listed as supporting Windows 7 and the release supports XP, Vista and Windows 7.