GRUB2 sometimes can't scroll

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http://chakra-project.org – I'm on a laptop with Chakra/Win7 dual boot.Today I found that I can't scroll down to choose Win7.The bar remains still at Chakra, which is the one I boot last time.So I cut off the power and boot again, and it only works after a few times of cut off and power on that I finally can choose win7I'm now under win7, to finish schoolwork that only support windows.Would you please tell me that any further info (log or some other things) should be provided?model: Vaio VPCEA16FWHD:/dev/sda1 system reserved/dev/sda2 recovery/dev/sda3 windows C:\/dev/sda4 extended /dev/sda5 data /dev/sda6 (HowTos)