Lockscreen bug

hi evereyone, i need some help to know what happens to me its a bug or is a normal problem on the iOS software... i wake up my iPhone 4s... slide away the slide to unlock button... it unlocks but exactly when the icons start to appear the screen turn off... its weird coz when i press the home button or wake button the screen turns on again and the phone wake in the homescreen and everything works... im on iOS 5.1.1 restored yesterday... and "Set up as New"

this weird issue happens like 1 to 1000 tries to make it appear, so its difficult to show it on a video or smth like that D:

someone know why this happens?... thx

 

ok i done it a few minutes ago, hope it will be solved