How to Fix Firefox always keeps showing "Restore Previous Session".

Today, my ubuntu crashed while I was using firefox. I rebooted and everything seem fine except one thing. Firefox show "Restore Previous Session" dialog everytime I open firefox.
Even though I've shut it down properly , the dialog keeps showing.

I googled around but I had no luck. I think that the problem is firefox config files may be some corrupted because of the crashing. So I went around in ~/.mozilla and try out some way and PONG! It's fixed! :)

Here is the solution.

1. $ cd ~/.mozilla/firefox/fwegtctl.defaults (you may change this to your firefox profile directory)
2. $ mv sessionstore.js sessionstore.js.bak
3. Restart the firefox.

Just simple. I guess that sessionstore.js saves the data about session (its filename tells that. HAHA) and firefox on opening will see whether this file exists or not.
Good Luck!
UPDATE : I've just found that there is another problem. The problem is the location bar doesn't update anyway. It's still stay blank or some url and when you change the tab it's doesn't effect. The location bar search feature also off. I don't know this problem and previous problem if it's an consequence. I spent a hour finding out the solution in the .mozilla/ (yes, again!)
at last, the solution is right down.

1. $ cd ~/.mozilla/firefox/fwegtctl.defaults (you may change this to your firefox profile directory)2. $ mv places.sqlite places.sqlite.bak
3. $ mv places.sqlite-journal places.sqlite-journal.bak

I hope that these soulutions will work for you.