Winlogon.exe application error?

This mornig when i logged onto my computer.. I got the
following error message

MCI command handling window: winlogon.exe - Application
Error
The exception Integer division by zero
(some hex value) occurreed in the application at location
0x10003e3b
Click OK to termiate the program
Click on cancel to debug the program

if i click either my computer just reboots.

I have done a full virus check and no virus was found.

I have installed just installed SP1a and all the latest
security updates...

any help would be great