I had the same problem with the HP Pavilion dm4 I started using this week.

I couldn't find any way to stop it from happening within apps. But I found that if you stop it from switching to the power saving adapter (See: http://h30434.www3.hp.com/t5/Notebook-Display-and-Video/I-wish-to-disable-Switchable-Graphics-on-a-DV7-4030ed/td-p/344302) that it stops.

Obviously this impacts your life on battery. But it's a fair tradeoff rather than losing the ability to use any open FF windows. At least until someone can declare a real solution.

@Ted_H Thanks for the link, I think however that this is a FF-bug to and hopefully there is someone there who can solve the issue! :)

There must be many people out there having our problem!