There were a couple AntiVirus/AntiMalware products that keep coming up, but I haven't validated that in the lab and don't want to call anyone out publicly without reporting the issue to them first. If you could tell me what antivirus/antimalware products and versions you have installed, that would be helpful.
So, third party stuff aside, I'd like to know more about the crashes your seeing:
1.) Please provide links to the Firefox crash reports. If you have multiples, the first few would be great.
In Firefox, type about:crashes in the address bar
If the link starts with "bp...", it's already been submitted -- just right-click on it and copy the link, and paste it into the reply here.
If not, click it to submit it, and copy the subsequent link.
2.) In firefox, type about:support
Just copy and paste the output into the reply.
3.) In Firefox, type about:plugins
Please copy and paste the output into the reply
4.) Please provide the output of the DirectX Diagnostic Utility
Click Start > type "dxdiag" [enter]
Click Save All Information
Copy the output of the file into the reply, or use Adobe SendNow/DropBox/PasteBin to share the file.
5.) If you can provide an exact URL and step-by-step instructions on repeating the crash (if it's consistent), that would be really helpful. My goal is to build out a configuration that matches yours as closely as possible, reproduce the problem and then debug it.
If you're not comfortable sharing that diagnostic information publicly, send me a private message. Just click my name and use the options on the right.