Vista Blank Screen Randomly

[No1ustad]

So I bought 3 Toshiba Laptops preloaded with Vista and each one has a blank screen come on randomly. The only button that seems to work is the power button.

I have McAfee virusscan installed and zonealarm. <- I've heard virusscan software may be the problem?

Anyone have any ideas on what to do? and if this would still be the problem if i upgraded to sp1 or downgraded to xp pro?

Thanks!!!