What I am assuming is that it has problems with the GNOME3, since gSharkDown works best with the gnome2.x versions and the libraries in the latest release of Ubuntu are newer. The other problem could be the integration in KDE, since I don't use it it will be very hard to investigate. Do you have the problem with an older version of gSharkDown? Are you using the package from the PPA repository, or the package provided in bitbucket?
You need to install pylast: sudo pip install pylast
Traceback (most recent call last):
File "gsharkdown.py", line 76, in <module>
from lib.enviroment import env
File "/usr/share/gsharkdown/lib/enviroment.py", line 6, in <module>
ImportError: No module named libproxy