Although I don't have a mod chip, I had the same thing happen when I was testing out points on my hard drive. The flashing 3 times and turning off is when theres a hard ware problem, such as the entire IDE cable isn't connected. Its a protection measure. So I think you could have
1) incorrect allignment
2) not in far enough
3) a cable that isn't in, and sometimes makes a good enough connection (ide, power, daughter board, ect)
I've herd this problem before, but I've never read an answer...