lvm2/dm hangs - ioctl cmd 9 failed

I'm getting various lvm/devmapper errors when creating and removing snapshots on debian Sarge.

device-mapper - ioctl cmd 9 failed: Cannot allocate memory Couldn't load device 'myvg-www2_snapshot'. Unable to deactivate logical volume "myvg-www2_snapshot"

I am using:

LVM version: 2.01.04 (2005-02-09)
Library version: 1.01.00-ioctl (2005-01-17)
Driver version: 4.3.0

or package names on sarge:

lvm2 2.01.04-5
libdevmapper1.01 1.01.00-4
kernel 2.6.10

My lvm subsystem is now locked by an unkillable process. I think the only option is to reboot, but I have a lot of data in LVM volumes, and don't want to risk losing it.

Has anyone else experienced these types of errors? Is there a bug fix for this?

There do not appear to be any updated packages for debian sarge. I could install from source, if I know this is a known problem with a known fix.

Thanks
Paul