Strange issue when closing the laptop lid in Windows 8

Hi!

My first post on these boards, hoping to get some help with an issue I've run into...

I got a laptop (Lenovo T420) which I've been running Windows 7 on for a while - everything has been working fine. Today I formatted my hard drive and did a clean install of Windows 8 Pro - working fine except for one strange but quite serious issue.

Whenever I open the lid of my laptop after having closed it (I've set it to "do nothing" when closed) the screen goes black for a second - then I get sent to the desktop and there is no mouse pointer showing - keyboard commands either doesn't work or behave strangely, and all I can do is do a hard reset and restart, upon which everything works until I close the lid again.

Would appreciate any help solving this problem, I'm not sure how to go about troubleshooting this kind of thing...