No need to cite the whole article (thanks!), so here's a short version: after upgrading from etch to lenny, bash completion would not work any more in this DomU:

# tail -f /var<TAB>-bash: /dev/fd/62: No such file or directory
-bash: /dev/fd/60: No such file or directory

Workaround:

# sudo ln -s /proc/self/fd /dev/fd

...or just install udev, although this package was not needed before the upgrade. Oh, there's a bug report for this one too.