I have uploaded the specification of the CD-ROM Combo drive SD-R2512 here. Thanks to Ricardo Cordeiro who provided me with the pdf file. You seem to need (at least) Acrobat Reader 6 (Windows) with Japanese Fonts (will download automatically) to view it.
The BIOS Update to version 0204A (original is 0203A) is available on the Asus Downloads page.
There is a BIOS Update for the M6800N that has a different DSDT. I have not tried it since I do not have Windows on my laptop to update the BIOS.
The CVS version of acpi4asus now supports the M6800N
Added Link to Andre Messerschmidts Page
I have solved my problems with genkernel which were reported by someone else in this bugreport. I do not have the time to finish this guide, so I have uploaded my kernel config here. This config was made using a 2.6.2 vanilla kernel, patched with the latest acpi4asus patch from here and the broadcom kernel patch that is part of the linux driver packages by broadcom.
Just FYI: the ACPI problems are still not solved with the 2.6.2 kernel.