usb and ethernet losing power, help

[RPGTyrant]

So when I start my pc up my Ethernet port as well as all usb ports working properly. Once the Windows Vista loading screen starts, none of the 10 usb ports work, and the Ethernet lights turn off. Didn't find another thread on this by a quick Google and Bg search, does this put up any flags to anyone for what this could be? More info in the spoiler if necessary.

Spoiler: show

I run Vista 64 bit, 650 watt power supply with a dvd, 3 hdd drives, quad core Pentium 2.8 ghz, 4 gigs ddr3 RAM and a radeon 4800 video card. I recently reinstalled Windows due to an error with a Windows update about a month ago, ended up killing my main Windows hard drive. Everything was working properly until I just got back from this vacation. I have blue screened twice in that period, and once again today while trying to get the usb ports to work. Windows is not yet activated online yet.

[Dmitry]

I had a similar problem where if I had devices plugged into my USB ports, Windows wouldn't boot up and would hang while loading drivers.

My first guess would be faulty power supply, but I wouldn't rule out the board either.

[Ezek]

Most likely PSU is dying or bad RAM. Run memtest86 on each stick at a time for 5-7 passes. Also, what is your CPU temperature readings under BIOS?