Comment 49 for bug 779166

Here is a workaround that did the trick on my acer 7715 with GMA4500 chip:

The following command has solved my problem.
"sudo setpci -s 00:02.0 F4.B=00"

The best is to have this command executed automatically at start up. You can do that by including that command in your /etc/rc.local file. To achieve this start up pc the pc with a 10.04 Live USB / Live CD. Go into the /etc/rc.local of the installed ubuntu 11.04 on your HD and insert "sudo setpci -s 00:02.0 F4.B=00" (without quotes) before the exit 0 command.

My rc.local looks like this:

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

sudo setpci -s 00:02.0 F4.B=00
exit 0

Hope this will solve problem.

Proudly copied from Angel Zone on:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/752165