I installed grub on a computer already containing Windows 8 Consumer
Preview. When I select the windows entry in the grub list, it displays
"Error: no argument specified; press any key to continue", and pressing
any key boots grub fine.

Searching the error message indicates that this is due to "--set" being
used instead of "--set=root" in the entry. Looking at grub.cfg, I can
see "--set=root" in the linux entries, but not in the Windows entry, and
editing grub.cfg manually to include "=root" in the Windows entry fixes
the problem.

The Windows 8 entry is displayed as "Windows Vista (loader)" in the list.
(To prevent confusion for those reading the attached grub.cfg)

Dear Maintainer,
I meet the problem after squeeze->wheeze upgrading when I boot windows 7.

Best wishes,
Alexandr

Hello.

As far as I understand, it is better to modify /etc/grub.d/30_otheros
and make update-grub after that. If you modify grub.cfg manually, it
will return back after update-grub (for example, after kernel
updating).