Comment 41 for bug 569841

Hey Dave,

Downgrading the kernel really isn't all that difficult. As a matter of fact, it took me more time to find the kernel and reconfigure GRUB 2 (I was familiar with the earlier version of GRUB) than it took to do the install. Here's what you'll need to do:

Download the kernel of your choice. I'm using 2.6.31-21, but it looks like 2.6.31-22 came out since then. I know for a fact that the former works . . . not so sure about the latter, so YMMV.

Here's a link to 2.6.31-21: http://packages.ubuntu.com/karmic-updates/linux-image-2.6.31-21-generic

Here's a link to 2.5.31-22: http://packages.ubuntu.com/karmic/linux-image-2.6.31-22-generic

Once you get the kernel downloaded, install it. It's just a *.deb, so it shouldn't be too hard.

After that, you'll need to edit GRUB so that it boots the older kernel by default. Otherwise, GRUB will keep booting the newest kernel and the problem won't get fixed. To do that, type cat /boot/grub/grub.cfg into a terminal and scroll until you find the section that contains the kernel you just installed (either 2.6.31-21 or -22).

Press Ctrl+Shift+C to copy the quoted text after "menuentry." Mine reads 'Ubuntu, with Linux 2.6.31-21-generic'.

Next, in a terminal, type sudo pico /etc/default/grub. Next to GRUB_DEFAULT=, paste the text you just copied by pressing Ctrl+Shift+V. This forces GRUB to pick that exact entry each time the computer boots. You could also control the default entry by entering the number of the entry (0 for the first entry, 1 for the second, and so on), but the number of an entry will change when you update kernels in the future. Setting the default using the exact name is much safer.

Also, you'll probably want to change GRUB_TIMEOUT= to something greater than 0. Punch in a (small) number to control how many seconds the GRUB menu appears at boot. I think it's helpful to have GRUB show up, even if it's only for a second or two. That way, if something goes wrong, you have easy access to alternate kernels, memtest, and recovery modes.

Make sure to run sudo update-grub after you finish editing /etc/default/grub. Restart your computer, and hopefully the kernel downgrade will fix your wireless issues. Be warned that swapping the kernel *may* mess up your boot splash screen. Everything will load properly, but it won't necessarily look pretty and you might get an odd error message or two. If that happens, don't panic. Just let it run its course and be patient :-).