Binary package hint: ubuntu-restricted-extras
In Ubuntu 9.10 Karmic Koala and LinuxMint 8 Helena, installation of ubuntu-restricted-extras to easily obtain MP3 playback and decoding, other audio GStreamer plugins, Java runtime environment, Flash plugins, LAME for audio encoding and to assist DVD playback, all plus Microsoft True Type Fonts, the basic installation failure of the latter results in Synaptic being stuck in a loop trying to run ttf-mscorefonts-installer every time that another package is added, which can be very frustrating.
Separate 'fixing' of the ttf-mscorefonts-installer problem would probably prevent this, easing document exchange, but meanwhile here is a work-around for all the rest of the packages required.
After ubuntu-restricted-extras locks up in a ttf-mscorefonts-installer loop, simply remove the ttf-mscorefonts package,
This leaves the other ubuntu-restricted-extras vital packages installed and allows the addition of other packages to proceed !