[ILUG-BOM] Screen brightness problem in ubuntu 10.04

Hello Everybody, This is my first post in the mailing list. I have Acer Aspire 4741Z laptop. After installing Ubuntu 10.4 everything is working out of the box. Only problem is I am not able to adjust screen brightness using Fn + left/right arrow keys. When I press those keys slider moves, but screen brightness does not changes. As brightness is always at maximum it drains battery fast. I have updated my distro with all latest patches and updates including latest kernel patch. But still have the problem. I even posted this problem on ubuntu forums also, but no luck there. Searched ubuntu forums also but found nothing. Is anyone else having same problem? Thanks in advance.