Proliant DL160 G5 health led blinking red

Hi everyone,

First of all I apologize for my English, it's not my mother language and I'll try my best to make you understand my problem. I've bought an DL160 G5 a year ago, on the second hand market. I upgraded it, 2 Intel Xeon X5472 processors, 12 GB FB 800 MHz ram, and 4 Samsung Spinpoint F1 320 GB (HD322HJ).
It worked well until yesterday, fans were getting really loud, and I decided to reboot the system. I didn't see any red led blinking because I rebooted it with VNC so I wasn't in the same room when the server was noisy. The server rebooted but during the first page of BIOS the led, normally green, blink twice red, and become green again. When the server come to the Ethernet boot agent page (press ctrl+s) fans speed decrease (as usual) but 1 or 2 second after that the server put itself on hibernation (power led amber) and the health led is blinking red. I tried to clear CMOS, check fans, try with only one ram dimm, one processor, no HDD, but results are always the same. When I disconnect a fan a POST error message appears (Fan 6 disconnected, or airflow insufficient), helping me to know what is the problem. Here there is no POST error message, I can't access to the OS, to the BIOS menu, so I'm a bit confused and I can't find the problem.

Does anyone have any solution for me ?
Thank you
Damien