Sorry about my English (I am from Germany).
I hope somebody can help me with this:

After I wake the computer up from the "energy-saving-mode" one of my hard
drives (I have 2) disappears from the list of my devices. Only the system
drive is left. It is a S-ATA drive that still remains, but the other one
(connected via IDE-cable) is gone. When I restart normally, it is there
again. When I shut down the computer normally, it is also there.

My system:

OS: Windows Vista Ultimate 64
Processor: Intel Pentium Core 2 Duo (2 x 2400 MHz)
Mainboard: Asus P5W-DH Deluxe

I also experianced that after the energy-saving-mode the computer does not
react on plug-and-play hardware via USB (external HDD, Headset, card-reader,
etc.).

I hope very much that you can solve my problem, I did not find anything in
the internet.

Thanks very much!
Ciao!