If, like me, you have added Miro’s repository to get automatic updates, you’re in for a bad treat; the most recent version has dependencies that are causing problems:
libxine1 (>= 1.1.4)
libxine1 (<< 1.1.8)
libxine1 (>= 1.1.7)
That is, as far as Synaptic is concerned, it won’t install Miro unless libxine1 is exactly at version 1.1.7 (why they could not just specify this as a single entry is beyond me). This is fine unless you’re using Ubuntu Gutsy with the backports repository in which case libxine1 is at 1.1.10 and prevents the installation of Miro 1.1.2-0pcf2 (1.1.2-0pcf1 worked fine BTW).
Hopefully Miro will release a proper package soon…