Aha!

You are right. Even though the drives were clean, I did an fsck from command line and received the following:

empeg:/empeg/bin# fsck -fay /drive0
Parallelizing fsck version 1.19 (13-Jul-2000)
e2fsck 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09
ext2fs_check_if_mount: No such file or directory while determining whether /dev/
hda4 is mounted.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
no room for private writable mapping
error: -12
fsck.ext2: Memory allocation failed while retrying to read bitmaps for /dev/hda4
empeg:/empeg/bin#

I would have expected a failed fsck to cause emplode to fail, but perhaps not. So I turned on swap, and will go from there.

Now, my question is: does emplode turn on swap when it attempts to fsck drives? If not, then other people with 80GB drives will start seeing this problem more frequently.