This ticket has nothing to do with OS; in fact, Lucid, being an older OS with an older kernel, is probably more likely to randomly panic on the codepaths we call than Squeeze.
Paths forward include debugging aufs, moving away from unioning file systems to something like unpacking chroots from tarballs, or moving away from using the aufs kernel patch to union mounts or overlayfs or unionfs_fuse or something. (But this ticket is separate from #463; we're interested in a different union solution in the clusters as well, and it may well be that a different solution like tarballs is the right answer for the builder and not for clusters.)