I posted in another thread that a dying SYSTEM disk in my WHS caused this issue.
Get a new system disk and install WHS as a rebuild (I think that's right, you'll see new installation or rebuild, restore, something like that, it'll be obvious...). If this does not do the trick you can always put back the original drive. This will NOT erase data on your storage disks.
And ironically, it was a PATA drive that caused my issue (used to be called ATA but now you kind of have to specify whether it's a P or an A). Since the min requirement for WHS is 120gb, I used an older Hitachi 160gb 7200 RPM drive for system. Mistake.
And don't be afraid to put more than 120gb as your system disk. WHS will use the remainder for storage.
Oh, and to test your storage drives, you have some work ahead of you. You will have to tell WHS to remove a drive, test, put the drive back and reconnect, tell it to remove the next drive, and so-on. This is going to take some serious time.
And you guys that do your own cabling, if you are old like me and remember only using wires 1,2,3, and 6; gigabit needs all 8. I've seen that before too.