Comment 31 for bug 509487

> /dev/mapper/sda2_crypt: UUID="m73M8R-p6Hn-okx2-xFFQ-eEKl-lKbZ-dq0qgK" TYPE="LVM2_member"

This should be sufficient to trigger /lib/udev/rules.d/85-lvm2.rules, which I assume you have on your system (since it's from the lvm2 package!). If you can run the commands from that rule's RUN variable by hand, it may be instructive; or to otherwise trace the set of processes running at this point. A good way to do this may be to edit /etc/init/tty2.conf to force a getty to start earlier in the boot sequence.