Immediate Crash will occur for Firefox 18.0.x, when hardware acceleration, Nvidia optimus, and Windows 7 Aero desktop are in effect.
If WIndows 7 Aero theme is turned off and changed to WIndows 7 basic then Firefox 18.0.x crashing stops.
This crashing is also happening with Waterfox 18.0.1
That link above is to my own previous question I had made. The thread was closed, so I couldn't add to it... but the issue is not resolved. I had thought I had found a solution, but I was mistaken.
Firefox 18.0.x (plus) hardware acceleration (plus) Nvidia optimus (plus) Windows 7 Aero desktop (equals) crash
Remove any of those items and crashing does not occur. For me I choose to turn off Aero.
Side note, I am enjoying significantly higher performance and better video quality in Netflix using Waterfox 18.0.1