Could be differences on what is considered earnings (some don't count one time losses or gains, like equipment or real estate sales or one time writedowns on inventory, and some do), could be outdated information that don't have the latest price or earnings numbers.

It's hard to say.

I've looked at a certain stock and my online broker has the P/E ratio of stock listed at 7.2, yahoo finance has it listed at 5.2, google finance (and a couple others) say nothing (losing money), another says 10, etc.

Any help would be greatly appreciated.