Can not unlock my LG optimus l7 p715

I am using LG optimus android phone. I have enabled screen lock in settings. then i switched off the phone. but when I switched on it again, it asks for the pass word to log in. and I have to type password to unlock the phone now. but keyboard is not popping up now. and screen time out is very less.but after touching several times on the editor I got the blank keyboard but I could not type with that blank keyboard. so I started restarting the phone. this time keyboard was popped up properly but keys in the keyboard are not working. so I tried connecting the phone to PC. but usb debugging is not enabled in the phone. so I could not connect to the pc also. so I pressed home button, volume up button, switch on button simultaneously but it was not working. Now I am trying to find the solution other than factory reset. please help me in finding the solution. thanks in advance.