I don't know why this is happening but for some reason Firefox now takes a very very long time to start up. Once it's running it seems fine. The only changes I have made were installing AVG 2013 (which i have removed to see if it makes any difference because I don' tlike these programmes running all the time), and updating Java plugins,. There is an issue with the Java Deployment Toolkit, whatever that is, but it's not set to be 'always activate'. That java update is the only thing I can think of. This is very frustrating because I like to have it running when i load up my pc.
It is possible that your security software (firewall, anti-virus) blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.
Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.