Since I only have the one SDRAM bar (512) I can't remove it to do the test you suggested but I did tighten the bar a bit, or at least push it down. I pressed the CUDA reset button like you suggested and the problem still seemed to occur - the article led me to another article that mentioned ...

I'm running 10.3.9 and have recently had problems booting up the computer. I backed up everything and reformatted the drive, ran the hardware test (which says everything is ok,) and ran clamX to check for viruses. The computer is still booting up sporadically, sometimes the light won't come on but ...