BleepingComputer.com: Windows Security Alert?

During the last couple of days or so I've been getting a Windows Security Alert that pops up, when I open Firefox, but not every time. The message is as follows:

To help protect your computer, Windows Firewall has blocked some features of this program.

Name: Firefox

It gives the options:

Keep Blocking

Unblock

Ask me later

Is this some kind of glitch? Where can I research this?

Any thoughts???

Thanks,
Tom