It's quite interesting since a big battle for SIS Chipset user < Notebook / Desktop > especially for onboard Graphics Card. The latest patch which is i post it on my old post is compatible until recent kernel so all of you shouldn't have to worry about getting a "black screen" or can't enter X-server for a while.
After quite for a couple of weeks, the SIS Bugs thread in launchpad finally got response from the X-org server staff and decided as Medium Bug. So it's a bright light for SIS user in future? As we know that SIS didn't give any support for Linux.
Here's for the discussion if you are interesting to read and it's started on 25 Nov 2008 :), It's 2years old case without any official solution.
SIS M671 Bugs - Launchpad.net