-> Do a MALWARE check with these Malware Scanning programs. You need to scan with all programs because each program detects different malware. Make sure that you UPDATE each program to get the latest version of their Databases before doing a Scan. Also, Close All other Applications (softwares) before Starting to Run Scans.

• Malwarebytes' Anti-Malware -> http://www.malwarebytes.org/products/malwarebytes_free
• SuperAntispyware -> http://www.superantispyware.com
• Ad-Aware Free Internet Security -> http://www.lavasoft.com/products/ad_aware_free.php
• Spybot Search & Destroy -> http://www.safer-networking.org/en/index.html
• Anti-Rootkit Utility TDSSKiller -> http://support.kaspersky.com/faq/?qid=208283363

Check and tell if its working.

The crash report for the Crash ID you reported,
https://crash-stats.mozilla.com/report/index/ea9f3e0a-c1a4-4e2e-abab-5a4f32120210
Firefox 10.0 Crash Report [@nsDocShell::SetupNewViewer(nsIContentViewer*)]
... refers to a related bug,

434403 NEW Startup crash (causes: Backdoor.Ulrbot.C Trojan, Spector Pro)

This crash can be caused by malware or by the "Spector Pro" monitoring software. Ref:

• Firefox crashes when you open it
• Troubleshoot Firefox issues caused by malware
• http://kb.mozillazine.org/Firefox_crashes#Spector_Pro_for_Windows

Doing all the various spyware scans seems to have solved the problem. I also added in a complete uninstall/reinstall for good measure.

All the various scans took more than a day, but it's been worth it.

Thanks!