I have problem to connect internet with natty. cannot, even ping router anymore

[dd]

Thanks a lot Sandy. Now I'm confused. Last night there's no connection at
>  all despite everything I did. Today I came back from work and suddenly I can
>  connect to Internet again. And I haven't done a damn thing!

this may be due to an automatic update of the router's firmware.
follow the 1st two posts of this thread:http://ubuntuforums.org/showthread.php?t=1753698&page=2  <http://ubuntuforums.org/showthread.php?t=1753698&page=2>
see, if it works for you...