fonts startup screen shows squares when doing maintenance check

Binary package hint: gnome-session

Ubuntu Lucid 10.04 LTS, upgraded from Hardy
gnome-session: 2.30.0-0ubuntu1
libpango1.0-0: 1.28.0-0ubuntu2.1
libcairo2: 1.8.10-2ubuntu1

Every now and then I suppose that the system does a maintenance checkup at (re)boot. Unfortunately I cannot see what is going on, because I only see squares. Esc does not help, ctrl-alt-backspace does not help either. There is no way I know how to skip this. The system is used for work and waiting costs precious time.

I already reinstalled all Pango packages, but it does not help.

Xorg.log says (clock is the same for all messages):

gnome-session[1340]: Pango-WARNING: failed to create cairo scaled font, expect ugly output. the offending font is 'DejaVu Sans 9.9990234375'
gnome-session[1340]: Pango-WARNING: font_face status is: <unknown error status>
gnome-session[1340]: Pango-WARNING: scaled_font status is: out of memory
gnome-session[1340]: Pango-WARNING: shaping failure, expect ugly output. shape-engine='BasicEngineFc', font='DejaVu Sans 9.9990234375', text='Lock Screen'
gnome-session[1340]: Pango-WARNING: failed to create cairo scaled font, expect ugly output. the offending font is 'DejaVu Sans 8.33203125'
gnome-session[1340]: Pango-WARNING: font_face status is: <unknown error status>
gnome-session[1340]: Pango-WARNING: scaled_font status is: out of memory
gnome-session[1340]: Pango-WARNING: shaping failure, expect ugly output. shape-engine='BasicEngineFc', font='DejaVu Sans 8.33203125', text='Not responding'
gnome-session[1340]: Pango-WARNING: failed to create cairo scaled font, expect ugly output. the offending font is 'DejaVu Sans 9.9990234375'
gnome-session[1340]: Pango-WARNING: font_face status is: <unknown error status>
gnome-session[1340]: Pango-WARNING: scaled_font status is: out of memory

For the rest I do not have font problems on that system.
There is a font error. It seems to mention two different DejaVu Sans versions, but the version on the system is a link in /usr/share/fonts/truetype/msttcorefonts to a font in the windows directory, which is mounted in fstab. Shouldn't gnome-session or pango fall back to another font? These messages should be readable.

Edit: not upgraded from Dapper, but from Hardy