I had this problem with mu asus 1000he. What I did to fix it was to go into the router settings and make sure it accepts wireless N which I beleive the asus is set to run on if not you need to change the setting of the asus itself to run on G. You can find more info on this and a better explanation by doing a search on the asus forum.
http://forum.eeeuser.com/viewforum.php?id=55 or eeeuser.com. Sorry I'm not tech enough to explain it more clearly.