Bootsector not writable?

[Andre Timmermann <debian.lists@darktim.de>]

Hello List,

I have got an Dual Opteron system from Siemens for testing purposes.

Here are the specs:

System: Siemens Celsius V810 
2x AMD Opteron 2.0 GHz
1 GB DDR SDRAM PC400 Ecc

Graphic: nVIDIA GeForce FX5200

Serial ATA Raid-Controller: Adaptec AAR-2410SA
3 x 80GB SATA harddiscs

I have got some problem installing any linx ditributpn on this system.
I have tried Gentoo, Ubuntu and Debian AMD64, but I was not able to
install the bootloader into the MBR of the harddisc (booting from a
bootable floppy works flawlessly)

grub-install works without errors:

~# grub-install /dev/sda
Installation finished. No error reported.
This is the contents of the device map /boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.

(hd0)   /dev/sda
~#

But when I try to boot the system, the bios shows "Operating system not
found"

I have disabled the write-cache feature of the RAID-controller and the
harddiscs itself, unfortunately it didn't help.

I decided to take a closer look into the MBR:
dd if=/dev/sda of=bootsector bs=512 count=1

When I open this file with a hexeditor, I can see the following message:
...GRUB .Geom.Hard Disk.Read.Error...

I do not know if this has something to do with the problem.

Any hints for me?

Greetz,
Andre