No key combination is working for me to recover: http://en.wikipedia.org/wiki/Magic_SysRq_key
It happens to other people:
http://askubuntu.com/questions/58412/why-is-ubuntu-unity-freezing-up-on-me-sometimes
Many other people:
There's a major regression in Drupal 7 compared to Drupal 6: the taxonomy/term/1,2,3 and taxonomy/term/1+2+3 style listing pages no longer work, coldly replying page not found.
This is very sad: http://drupal.org/node/503456
My naive issue 'hey we missed this' http://drupal.org/node/1028556