Which version are you playing? Try updating to the latest version!
well... i'm playing 0.66, and in this version, there is a bug with the character looking up.
Please try updating to 0.66C.
Okay, thanks for your help, I'll give it a try.
It's now confirmed that the Shift key stops working when a game controller is plugged in. If you're playing with a controller connected, try unplugging it and see if that helps.