I don't know about the OP, but in my case, with the Pix boxes, the power supply issue seems to be the connection on the circuit board. If you touch the power wire in any way, it jiggles the connection inside the box, and interrupts the power.
I am sorry to hear about similar problems with the ASA 5505, as I have two of them to replace two defective Pix 501s. Out of three initial purchases of
501s, one has a loose power connection at the board, and one suddenly stopped all connections to the inside ports. I too am disappointed with the quality of the Cisco products that I have purchased so far.