bf stands for boot-floppies, which is what the Woody installer is called. It's a generic kernel with no machine-specific optimizations.
The kernel-source-2.4.18 was patched recently. If you do
apt-cache show kernel-image-2.4.18-bf2.4
You'll see that it has:
Which is what you want, correct?
apt-get update again, and apt-get upgrade. Maybe the mail beat the deb to the servers. I dunno to be honest. But hopefully apt-cache show will help you in the future...