i had this as well, i uninstalled opera, firefox and a bunch of other apps and i did an apt-get clean, apt-get autoclean and apt-get autoremove....

it only freed up a little over 2mb (42mb) but 1.2 installed fine afterwards...

i wonder if opera and/or firefox is incompatible with 1.2 as even though the repos are still enabled i do not see them in the download list anymore! bummer....