What is wrong with my Firefox Browser?

It will not open at all. When i attempt to open, it says that there is an error and prompts me to send a report. I thought it might be adware or spyware, but I have McAfee and AVG. Both scans show nothing. In the meantime it says that it may have to do with my proxy settings, but I am not running any proxy's......I have cable. I've started using Opera and it is fine along with my internet explorer. I just want to know what it is and if it is affecting any other part of my PC. HELP

What is wrong with my Firefox Browser?antivirus protection

If you have Yahoo Messenger loaded on you computer, you may have a problem with Firefox.

The latest Firefox always would crash on me when I visited my Yahoo! Mail. One possible reason is the bug caused by the stand alone Yahoo! Messenger application. The Yahoo! Application State plugin must be turned off for Y-mail to work properly.

Try the following:

(1)Type "about:plugins" in the Location Bar of your Firefox browser and press Enter. A list of installed plugins should come up.

(2)Look for "Yahoo! Application State" ("npYState.dll") in the installed plugins list.

(3)If the file is listed, close Firefox completely. Open the C:\Program Files\Yahoo!\shared folder then rename the file "npYState.dll" to "XnpYState.dll". This will disable the plugin.