That sounds suspicious. Does it look like a scare-tactic ad to get you to call a toll-free number for support? There are a lot of scams like that around the web which you can click into accidentally. Often when you see that screen, pressing the Esc key several times in a row quickly will break the cycle of the popups and let you close the tab normally. Closing the tab normally helps avoid the problem of getting the tab back after crashing out of Firefox. In Some cases, there will be a checkbox near the lower right of the popup which lets you tell Firefox you do not want to see any more dialogs from that page. If you get that one, check the box and click OK to break the cycle. If none of that helps, can you capture a screenshot of the problem dialog/page? This page has tips on how to do that: [[How do I create a screenshot of my problem?]] Please cut out or blur any sensitive information in the image before attaching it to your reply. Thanks.