I use Gephi to finish my Bachelor thesis, but with recent system updates, it stopped to work.
I only got a screen which hangs on "loading cached objects", and then silently quit leaving no error messages.
It took me a few days to solve the problem. It was Java's fault. Dowgrading my system to Oracle's Java 6 SDK made gephi work again.
If you don't want to downgrade your entire system, you can just edit the /gephipath/etc/gephi.conf file and replace the variable jdkhome with your local installation of Java's SDK.
Hope this helps ;)