The internal wireless card is an Intel Wireless WiFi Link 5100. The driver used by default is iwlagn. There is mention of iwlwifi being good for injection.

But injection works, to some not-clearly-understood-by-me extent, with the default drivers. But other stuff fails, and it's necessary to patch the drivers with compat-wireless to get stuff working properly:

From Jay Scott:

wget http://www.orbit-lab.org/kernel/compat-wireless-2.6-stable/v2.6.37/compat-wireless-2.6.37-4.tar.bz2
tar -xvjf compat-wireless-2.6.37-4.tar.bz2
cd compat-wireless-2.6.37-4
wget http://patches.aircrack-ng.org/channel-negative-one-maxim.patch
patch  p1 < channel-negative-one-maxim.patch
make
make install
su
make unload

Put wlan0 into monitor mode:

airmon-ng start wlan0 1

The 1 referring to the channel you want to monitor

Interface   Chipset          Driver
wlan0       Intel 4964/5xxx  iwlagn - [phy0]
                             (monitor mode enabled on mon0)