Hello, after having this problem , i was able to resolve it. It might be the same case for you. Here is how to check: If you have (had) norton antivirus, and specifically if you uninstalled it, it is for sure what is causing IE and Firefox to not work. Follow these steps if you uninstalled norton:
1- Download and Run norton removal tool : http://service1.symantec.com/Support/tsgeninfo.nsf/docid/2005033108162039
2- restart your computer.
3- check if the browsers do
4- If they do, thank me at [email]richard_chaaya2@yahoo.com[/email] :)