Hello Shannon.

Your network may have been hacked. You should look into it or contact your network administrator as soon as possible.

This is a security feature and Firefox is letting you know that something is wrong. I take it it only appears on https sites (on all of them), so I urge you not to use them in any way! Not in Firefox, not in any browser, until this issue is resolved.

If you're at home, you can factory rest your router. That should fix the issue.

Also, and by the way, Firefox 3.7 will probably have a more comprehensive error message that informs people better of this kind of errors and what is happening. That should reduce confusion from users.

Again, do not use secure sites until this is fixed! Don't put your password anywhere, don't access your bank accounts or anything relevant at all! First, make sure this is fixed.