Unless this was a rare virus that affects the BIOS, I think this is a coincidence. I don't think there are any trojans that can affect the POST. I think it is more likely that either somehow your CMOS settings have become corrupted or you have a problem with your RAM. I suggest that you carefully check the CMOS settings, or reset the CMOS and start again. If that doesn't help, then if you have more than 1 stick of memory, try with just one at a time.