I did a clean installation of Ubuntu 14.04.2 two months ago and I noticed recently that firefox was stuck at version 36. I uninstalled it and then the system showed version 35 as the latest. The same applies for some other packages like compiz-plugins which I cannot install because it is stuck on an older version and conflicts with other compiz packages. The system complained many times about held packages before that. I tried fixing broken dependencies but no luck.
What can I do?