My 1 year old homebuilt system is having a problem I've never seen before anywhere. For a couple of weeks now it will occasionaly forget it has a network card. I checked the system tree under control panel and it is not even there, no yellow "!", no red "X", just completely missing. I have to completely cut power to the box to get it back.

Just a few days ago, it did the same thing with both of the hard drives. I booted it with a Ubuntu live cd and cannot locate the drives under gparted or in the BIOS. I reseated the connectors and the drives came back.

Also, now it sometimes won't turn on at all, no fans, no POST, nothing. This also gets resolved by completely cutting power to the box.

What is going on here? Is my mobo going bad? If so, what is a good replacement for an ASUS P5B-E?

Processor: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz (2 CPUs)
Motherboard: ASUS P5B-E
Memory: 2048MB RAM
Hard Drives: 250 GB X2
Video Card: EVGA 8800

What PSU are you using?

Power supply
HIPER HPU-4M480-PS ATX12V v2.2 480W Power Supply - Retail
Item #: N82E16817128005

get a new psu hiper are rubbish, it would explain why your system is not posting, about ur drives i would guess a lose connection on your mobo or on the HDD's, to resolve the network issue i would try updating your bios (AT YOUR OWN RISK)

I checked the CMOS battery, which read a healthy 3 volts. Then I replaced the PSU with a Thermaltake 430W. All seems to be sweetness and light again.