Novell Zenworks 10 Imaging cannot handle ext4fs

When trying to create images of either an Ubuntu Karmic or a dual boot Windows XP/Ubuntu Karmic installation using Novell Zenworks 10 Imaging, we consistently got the nondescript 'error 32' from the imaging server. Googling for the error number doesn't get us any further than a vague post on a Novell forum that it's perhaps something network related. However, the logs-in-RAM on the machine creating the image indicate EXT3-fs: "couldn't mount because of unsupported optional features" about a couple of Linux partitions.

And lo and behold, when we recreate the Ubuntu installation with with a preseed file that contains

partman-base partman/default_filesystem string ext3
    

, then Zenworks can suddenly create an image all right.