Hi,
It sounds a "hardware" problem, while both systems (Win and Ubuntu) shows 100% rare core working. So there's nothing to do with the OS. What I would do is to update your BIOS version, if there's a new version, look at that and put bios configuration on default. Good idea also to change CMOS battery (don't fotget to disconnect power cord, extract the back battery and press ON 30 seconds before change it).