If you encounter the recently virus spread on WindowsXP like LSASS or BLASTER, to avoid this problem and to fix the error, first you have to do is to stop the "TIME BEFORE SHUTDOWN", because 60 seconds is not enough time to fix error.

[START] > [RUN] > [ shutdown -a ] meanwhile, the dialog will be gone.

and please visit HKCERT to get the latest virus information and fix tool on that site.