Duemilanove red light

Hi I have an Arduino Duemilanove that I had put grbl 0.8c onto and working fine with 3 steppers running fine on the workbench. I switched it off and left for a few days and then when I switch it on I get green power led and the red led marked L (D13) and if I try to program it it fails every time any idea's PLEASE. Cheers Bill