Well, I got it to work, but don't know why it worked.
I renamed the udev riles file to another name.
# mv /etc/udev/rules.d/50-kqemu-rules /etc/udev/rules.d/10-local.rules
bash-3.1$ ls -l /dev/kqemu
crw-rw---- 1 root qemu
10, 57 2009-09-28 01:24 /dev/kqemu
I assume it's somehow related to this:
Files in /etc/udev/rules.d/ are parsed in lexical order, and in some circumstances, the order in which rules are parsed is important.