Acer Aspire 7530 mysterius problem

Hello, I have an Aspire 7530 with a strange problem. The problem is that when it is power on for the first time (in cold status) the mashine boots up normally to Windows Vista and let you working normally. When trying to rebbot it does not reboot (it is just shut down). After that when you press the power button the power led flashes for a second and then shuts down. In second or third attemp it is power up (leds are on) but after post screen does not show anything. I had ordered and change motherboard twice, but the syptom is the same. I also have change the CPU fan and RAM modules with new ones. The same with another working CPU. Have tried, also, to power up with minimum peripherals (without wirelless card, GPU, modem, even without connecting the switches for network which are on the left side), but still the same. Please none that had also check HDD in another pc and it is working perfect, and have checked the system with Eurosoft PC Check (includes in Hirens boot CD 10.0) and passed all tests.
I have tried also to flash the BIOS. Downloaded the BIOS from ACER side, (all versions), but when trying to flash it (with any version) i receive an Error message with error code -1. (could not find something in google regarding this error).
So I'm desperate i don'nt know what else to do. If anyone could help me would be much appreciated. Thank you in advance.