Internet acting funky....works on IE, but not on Firefox

[winner2000]

So on my family home computer, when we try to use the internet via Firefox, every site (hotmail, MSN, youtube etc.) says "Page Not Found". However, the IE browser opens up everything perfectly and everything runs normally (which means the internet connection seems to be fine). I tried to upgrade Firefox to the latest version but still no dice.

Anyone have any suggestions I can try out to fix this?

[kcorscadden]

Clear your cache

[Fahrenheit]

Also checked your proxy settings.