I upgraded Linux kernel from 2.6.15 to 2.6.17 and found out that the weekly backup process appeared to hung the whole machine. I narrowed the problem to when the snapshot volume was being removed:
lvremove /path/to/snapshot/volume
I found this email that describes a workaround, but the more proper workaround is to upgrade sarge's lvm2 package made available by Juergen Kreileder.
(originally from http://microjet.ath.cx/WebWiki/2006.09.04_DebianSarge_LVM2_Linux2.6.16.html)
