There are many Bittorrent client in Linux and, under Ubuntu (and this is surely true for other Linux distributions too), most of them depend on a library called libtorrent.
Under Ubuntu 12.04 LTS, libtorrent is buggy and causes Bittorrent clients to crash on a regular basis. The solution is, of course, to upgrade libtorrent from 0.15 to its latest version 0.16. The way to do that is to add the ppa:surfernsk/internet-software PPA and upgrade the whole system:
sudo add-apt-repository ppa:surfernsk/internet-software
sudo apt-get update
sudo apt-get upgrade
Doing that upgrades python-libtorrent to 0.16 and installs libtorrent-rasterbar7. Removing libtorrent-rasterbar6 (which is not needed anymore) is simply a
sudo aptitude remove libtorrent-rasterbar6
Since doing that, Deluge, the Bittorrent client I use, hasn’t crashed at all. Life is cool.
(Solution obtained in the Deluge forum)