a few days ago my phone stopped asking for the unlock pattern after i put it into screen off mode or leave it sitting for a while. if the screen is blank and i hit the button it simply comes on and any one can do anything with it. sometime i notice that it shows the pattern unlock for a brief moment then it it just goes away. the phone WILL ask for the pattern if i power off and power on only from a powered off state not from a sleep or screen off state like it used to. I have attempted to pull the battery and i have done a factory reset both with no results. I have attempted to set it to password or simply turn of screen lock and turn it back on. all other functions of the phone are working fine, (calls, texts, data, etc) does any one have any idea what may be the issue?