Comment 16 for bug 732038

Oh, wait, you installed just one deb file. Maybe that's why :) You have to install 3 files.

http://kernel.ubuntu.com/~kernel-ppa/mainline/daily/current/

linux-headers-2.6.38-999_2.6.38-999.201103291240_all.deb
And for i386 (for amd64 the other 2 instead of those):
linux-headers-2.6.38-999-generic_2.6.38-999.201103291240_i386.deb
linux-image-2.6.38-999-generic_2.6.38-999.201103291240_i386.deb

sudo dpkg -i *.deb

Anyway, I did the test so I don't think it's still necessary to do it too.