Bug#612439:

[Daniel Black]

I had the same problem an did a successful restore on a live system as follows:

apt-get install linux-source-2.6.32

This involved copying 5 files from the 2.6.33 kernel.org release in the directory drivers/md :
dm-snap.c
dm-snap-persistent.c
dm-snap-transient.c
dm-exception-store.h
dm-exception-store.c
One change was needed in the dm-snap-persistent.c INIT_WORK_ON_STACK -> INIT_WORK on line 257.

in the 
cd /usr/src/linux-source-2.6.32

cp /boot//config-2.6.32-5-amd64 .config

make -j4

rmmod dm-snapshot
mv /lib64/modules/2.6.32-5-amd64/kernel/drivers/md/dm-snapshot.ko /lib64/modules/2.6.32-5-amd64/kernel/drivers/md/dm-snapshot.ko.orig
mv drivers/md/dm-snapshot.ko /lib64/modules/2.6.32-5-amd64/kernel/drivers/md/dm-snapshot.ko
depmod -a
modprobe dm-snapshot

After that the lvchange -ay {volume} worked.

Though there's a reasonable amount of code change there in dm-snapshot most of it is adding the merge to origin code and the rest is unaffected. I'd do further comparisons against later kernel versions to see if there's any regressions but for the time being this fixed my problem.