May I suggest you have a look at firefox crashes that gives suggestions with links to other articles as to what may be tried & types of crash situation together with an explanation of how to obtain crash IDs; that may help in figuring out the reason for the crashes.

Try to install the latest Firefox release version as you seem to be on the beta update channel.
Your system details list suggests that you use a Firefox 9 beta release (installed Dec 5,2011).

You can find the latest Firefox release here:

• Firefox 9.0.x: http://www.mozilla.org/en-US/firefox/all.html