After an update the trick was lost so I changed the following line in the file /etc/default/grub
GRUB_CMDLINE_LINUX="quiet"
to
GRUB_CMDLINE_LINUX="quiet acpi_osi=\\\"!Windows 2009\\\""
It works fine for Fn F8 and there are no more problems with update-grub
Adding acpi_osi=\"!Windows 2009\" at the and of the "linux" line the Fn key works again.
Thanks a lot for this work around!
(Notebook: Dell Precision M2400, Ubuntu 10.04 x64)
After an update the trick was lost so I changed the following line in the file /etc/default/grub LINUX=" quiet" LINUX=" quiet acpi_osi= \\\"!Windows 2009\\\""
GRUB_CMDLINE_
to
GRUB_CMDLINE_
It works fine for Fn F8 and there are no more problems with update-grub