slackware 10 shutdown issue

Im running slackware 10 dual booted with Xp/sp1 on my laptop, recently i have noticed an issue when i tell the linux box to shutdown

using shutdown -h now

usually prints a lot of data to the screen, which run level, stopped devices etc and then powerd off the box. recently though the screen blanks and it doesnt power off correctly.
any suggestions?

Code:

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modprobe apm
shutdown -h now

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This is probably more of a Tech Board question, though. :)