If you upgrade to libpam-modules 0.72-15 in unstable, you *must* comment out all occurrences of pam_limits.so in files in /etc/pam.d, or any services that use that will break. On my machine, this hit cron, gdm, login, and ssh; fortunately I hadn't logged out in the meantime. See bug #88401 for the details.
Cheers, -- Colin Watson [EMAIL PROTECTED]