safari 5.1.9 quits

I'm running Snow Leopard with Safari 5.1.9 and it suddenly won't run. I'll open safari, the apple home page comes up then it quits. Even if I go to open another web page it quits. I've check for software updates and have them up to date. I've also have done the "verify disk" process through the Utilities with it saying everything ok. Not sure what has happened for this to start up suddenly when it had been working ok. Have now added Firefox from another MAC to be able to get on the internet.