Inconsistent failures to resume from hibernation / suspend-to-disk on a Thinkpad T61

[Celejar <celejar@gmail.com>]

I recently installed Squeeze onto a T61. Hibernation (via the
'hibernate' command, or 'pm-hibernate') always seems to work, but the
system doesn't always come back up. The first time after a reboot it
seems to always come back, but it often / usually fails the second or
third time. I'm running amd64, and I've had the same problems with both
the Squeeze 2.6.32-5-amd64 kernel as well as the 2.6.39-bpo.2-amd64 from
backports.

I never get any sort of progress report, but when the system comes up
properly, first the cursor flashes large (console, no framebuffer
style), then I get a beep (or several), the cursor shrinks to
framebuffer size, and then the system comes back. When it doesn't, the
cursor stays large, and there are no beeps. [I usually try from within
X, but I'm pretty sure I've seen the same problem when trying from the
console.]

I've checked /var/log/pm-suspend, and there's never anything there past
a report of successful hibernation.

Hardware info:

Intel GM965 graphics
Intel PRO/Wireless 4965 abgn
2 GB RAM

FWIW, I'm currently running the system without any battery.

Hibernation is to a swap partition. Disk is partitioned with /boot on a
primary ext3 partition, and everything else on logical volumes of an
LVM volume group atop an encrypted (dm-crypt / LUKS) volume atop a
second primary partition.

Any ideas, fixes, or troubleshooting suggestions?

Celejar <celejar@gmail.com>