I installed Oneiric as a guest OS in VirtualBox using the Mini CD. I installed the ubuntu-desktop package and everything seems to work fine - well, except for a font issue with the terminal:

As you can see, some of the letters overlap and it's difficult to read. I checked the settings and it the checkbox "Use the system fixed width font" is checked with "Monospace | 12" selected underneath it.

Edit: running the commands mentioned in the comments:

$ fc-match "Monospace"

DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"

$ gconftool --get /desktop/gnome/interface/monospace_font_name

Monospace 10

$ debsums ttf-dejavu-core

/usr/share/doc/ttf-dejavu-core/AUTHORS                                        OK

/usr/share/doc/ttf-dejavu-core/BUGS                                           OK

/usr/share/doc/ttf-dejavu-core/NEWS.gz                                        OK

/usr/share/doc/ttf-dejavu-core/README                                         OK

/usr/share/doc/ttf-dejavu-core/changelog.Debian.gz                            OK

/usr/share/doc/ttf-dejavu-core/copyright                                      OK

/usr/share/doc/ttf-dejavu-core/langcover.txt.gz                               OK

/usr/share/doc/ttf-dejavu-core/status.txt.gz                                  OK

/usr/share/doc/ttf-dejavu-core/unicover.txt.gz                                OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans-Bold.ttf                      OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf                           OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSansMono-Bold.ttf                  OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSansMono.ttf                       OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSerif-Bold.ttf                     OK

/usr/share/fonts/truetype/ttf-dejavu/DejaVuSerif.ttf                          OK