The top of the lease states: Lease Contract only valid if filled out before January 1, 2008. I signed the lease in March 2008, could this mean my lease is invalid and could that be grounds to get out of the lease

If you're looking to break your lease for a totally unrelated reason, I highly doubt any judge would let you do so for a reason like that.

Why don't you tell us where you are located and give us some additional details about what you're wanting to do and why. Then we can give you a more informed opinion.