Windows Defender fails to initialize

[Guest Captain Henk]

Running Vista Home Premium. Lately when I boot the PC, I get a message box

that states: "Windows Defender failed to initialize". But when I go to the

Security Settings and open Defender it 'appears' to be running. I checked

my FW/AV (Zone Alarm Security Suite) and also ThreatFire, and they do not

appear to be blocking anything related to Defender.

Any ideas or input would be greatly appreciated.

Henk

PS - I have tried to do an update but there are none that show.