WFM on FF7, FF8, FF9 and FF10. But I don't know what "browser issue" would mean. That's like saying "I can't catch a breath" and someone says "That a breathing issue".

Here is the ENTIRE error message I get after clicking on sign in: You may be experiencing a problem with your browser

The problems you are experiencing are most likely the result of Web filtering software, firewalls, popup blockers or ad blocking software.

You may resolve this issue by visiting your browser's website and searching for instructions on temporarily disabling Web filtering software, firewalls, popup blockers, and/or ad blocking software. You may also use another computer.

For Internet Explorer http://support.microsoft.com For Firefox http://support.mozilla.com/en-US/kb/ For Safari http://www.apple.com/support/

Important These actions may increase your security risk. Your computer or your network may be more vulnerable to attack by malicious users or by malicious software such as viruses. We recommend that you address any concerns with your browser's support team.

Did you check to see if you have any of those issues.

1.Check for Malware
2.Check that you are not blocking Verizon with popup blocker or filter tools.

Don't know why they said Firewall, that would be blocking FF from the Web not Verizon.

If you think it is something you did in FF and can't remember, you could use a new profile to check. New Profiles - Where Firefox stores your bookmarks, passwords and other user data will set FF to default.