My iPhone wont let me type in my password please help?

your passcode?
your iphones mental
mines not

Same thing is happening to my iPhone 4. If you have jail broken your iPhone (tethered) on firmware 4.2.1 you simply shut it off, connect to PC, run redsn0w, check off "Just boot tethered right now". Fallow the steps and that should do it. If you are not jail broken and running on 4.2.1 you can try force shut down by holding down the power and home button for about 10 seconds. If that does not work you will have to restore your iPhone. You will have to use the computer you have you phone backed up to because if not your iPhone will deny connectivity to your PC because of the passcode. If none of these work you have to call apple 1 (800) MYAPPLE. if you are not on 4.2.1 you should not have this issue because it is an iOS 4.2.1 bug.

My iPhone 4 does it too! it does it if your passcode is a word.... its beacuse the gyroscope detected a "shake" most likely when you took it out of your pocket... and intiated the undo action... simple apple glitch with no fix... you have to receive a call for it to fix..... i really hope 4.3.3 will have a fix..