WinME machine, k6/II 500, 128Mb, ASUS P5S-VM.

System works fine after format and reinstall. Shutsdown perfectly. Installed an ASUS WL-138G wireless PCI card. It works just fine. But, the PC wont shutdown then. The card works fine in any of the other machines here, but not this one. I've tried changing PCI slot, updating drivers etc. Is there a setting or some such somewhere for this that ive missed. BTW the machine wont boot with the card in PCI slot 3 (of 3).