Ubuntu – Why are letters overlapping in the terminal

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