Grey screen?

My macbook was asleep and when I opened it the screen was grey and had verticle white lines. Nothing was happening so I pressed the power button. It's working fine now, but I'm just wondering why that happened?

Thanks

Possible the sleep/freeze problem that has been rectified via your system update tool which you are able to download?

Give it a download?

Liam

Infact, that problem looks like it's just for iMac machines, not macbook.

Apologies