can't get past nexus 7 password to load

[ceerbee]

I opened the case of my google nexus 7 and was greeted as usual with a blank screen, I pressed the power button but nothing happened . I held the power button in for approx 10 seconds and it started to power up with the name google appearing then the coloured cross glowed for a few seconds. I was then greeted with the keyboard on an unfamilier screen with the android logo saying enter your password with 'to unlock data storage' at the top. on the usual first screen I didn't use a password but had chose to use a pattern to unlock the tablet. Can anyone suggest how I can get past this screen as I can't see how I can put the required pattern in if that's what's required at this stage.