Every time I tried to log on to my yahoo email account, this message keeps coming up and it is very frustrating.
There are other things that need your attention.
Your above posted system details show outdated plugin(s) with known security and stability risks that you should update.
You can check if there is a file NPSWF32.DLL in the C:Program FilesMozilla Firefoxplugins folder and remove that file.
Update the Flash plugin to the latest version.
Update the Java plugin to the latest version.