Ok so i unplugged the modular pci-e connector (i leaved the first hard wired one to the card) and i used the molex to pci-e for the second one.

And OMG no shutdowns anymore! It was the PSU after all. With the card at stock values of course.

Now my only question is if it is safe to leave it that way or i should buy a new PSU a.s.a.p? I am not planning to installing anything new to the system besides maybe upgrading the RAM from 2gb to 4gb (i was thinking to buying two more sticks of the same RAM instead of buying two new 2x2 gb sticks, so i can keep the old sticks)

Either way thanks everyone for the help.