To complete a Timing Belt but I'm Stuck!

I was replacing my timing belt now...

My camshafts top dead center marks aren't aligned with my crank shaft top dead center marks. It's off by about a half inch. I can't turn the engine past a certain point now. When I took off the old belt it all matched up I may have accidentally turned them when I put on the new timing belt.

What do I do?

Take the belt back off and start over.