Comment 60 for bug 190664

I believe you have to download the 2.6.26 source code, then patch it to 2.6.27 from kernel.org

Use KernelCheck, it will make your life easier.

http://kcheck.sourceforge.net/
Run it as root/sudo, expand "More Information", "Latest Kernel Prepatch" should be some sort of 2.6.27.
Expand "New Kernel Patch Options" and select "Development Prepatch". Now click "Program" in the menu bar and select "build new kernel". It will automatically download necessary source code for you, run xconfig, and compile it.
During the xconfig stage, be very carefull to select the correct configuration, as I saw that the automatic configuration was not correct for me. The most important thing is that for iwl3945 to work, mac80211 needs to be enabled (dont remember where that option is, somewhere under networking). Save the configuration, close the window, and then go take a coffee break while the kernel compiles. After you install it, you will probably have to reinstall graphics card drivers.