pcr - problem in pcr (Dec/24/2010 )

I started pcr for my thesis last month and I can got an acceptable reply from it.But now it dont work and I dont know what is the problem?
does Anybody help me?

Can you tell us more about this PCR? Are you using a different DNA template?

When problems like this happens it usually is caused by the template degrading.

Very thanks. My object is investigation genetic polymorphism in Iranaian population and I have different dna from hearty sicks.