Scheduled Scan - Bugs?

I have some scheduled scans and at the end of the scan the computers are supposed to shut off. There are a few machines that do not obey this and keep running after the scan completes.

I am using BPP console version 1.1.132.15 / DB version 1348 / Client version 6.0.1373

The machines are running Windows XP Pro SP3 on a domain.