[CentOS] Second Xen NIC not being recognized?

I've got a Xen domU running Centos 5.2 (dom0 is also Centos 5.2) with two NICs configured. Both NICs show up in the Xen hardware details display. Looking at dmesg output from rebooting the domU, I see both eth0 and eth1 appearing there. But network configuration only knows about eth0, the one that was installed originally (eth1 was added later). There's options to create another NIC in network configuration, but "xen virtual ethernet" isn't one of the hardware types I can choose, and choosing the default doesn't give me anything that works.

Should I try reinstalling the domU with the NIC already in place? But even if that works -- shouldn't it be possible to add a piece of hardware to a system and have it recognized on reboot?