If your resolution wasn’t detected properly then you should try this this bugfix release:

Furthermore a user reported that he had problems on Debian Sid (because of a different Python release) and he had to:

type:
dpkg -i –force-depends-version urandr_0.1-0ubuntu7_all.deb

and edit /usr/bin/urandr, replacing
gksudo python randrgtk.py
with
gksudo python2.5 randrgtk.py

NOTE: I’m NOT recommending such method and I promise that I’ll look into this issue.