Live: No persistent storage on Mac

Binary package hint: casper

I am not able to use persistent storage with the Live CD (natty-desktop-amd64+mac.iso from 2011-03-29.1) on a MacbookPro6.2. I suspect this to be a Mac problem, because Mac handles partitions differently.

I created an ext2 filesystem on a USB system, labelled it casper-rw and booted with the USB stick in.
/var/log/udev shows that the partition is identified, but it doesn't seem to ever get mounted. Files saved e.g on the Desktop do not persist.
I also created an ext3 filesystem on the local disk, in case it was simply a problem with the USB stick. This also did not work.

This is significant, because the standard method of making a bootable USB stick with some persistent storage does not work on Mac (for reasons that I don't understand). I.e. the only way it seems to have persistent storage with a live image is by having a live CD and and an additional USB stick.

This is casper-1.259

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: casper 1.259
ProcVersionSignature: Ubuntu 2.6.38-7.39-generic 2.6.38
Uname: Linux 2.6.38-7-generic x86_64
Architecture: amd64
Date: Tue Mar 29 18:48:36 2011
LiveMediaBuild: Ubuntu 11.04 "Natty Narwhal" - Beta 1 amd64+mac (20110329.1)
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: casper
UpgradeStatus: No upgrade log present (probably fresh install)