2.6 LVM problem

[Andrew Ingram <andrew@uk.clara.net>]

I have a box which runs 2.4.22 just fine but wanted to try out 2.6.5 as
some of the extra features from 2.6 would be very welcome. The box has
several "normal" partitions (ReiserFS) and one partition that is
configured with LVM (for future expansion, at the moment it's just one
partition on the main HDD). Compiling and installing the 2.6.5 kernel
was fine. However, when I came to run lilo after adding the entry for
the new kernel in lilo.conf, I got the following message:

/dev/mapper/control: open failed: No such device
Is device-mapper driver missing from kernel?
Warning: '/proc/partitions' does not match '/dev' directory structure.
    Name change: '/dev/lvma' -> '/dev/vg00/mythtvlv'
Added 2.6.5
Added 2.4.22-HT *

Device mapper is installed in the kernel. Some googling showed that this
was the sort of message that people using DEVFS in their kernel
experienced. I'm not using DEVFS however.

Rebooting and selecting the new kernel resulted in the machine booting
just fine, but the lvm partition wasn't mounted. The error during bootup
was:
mount: /dev/vg00/mythtvlv is not a valid block device


Can anyone tell me what is going wrong here? I can post my .config for
my kernel if that would help.

Thanks,
Andrew