When I look up the IP address 239.255.255.250 I get this information:

Addresses starting with a number between 224 and 239 are used for IP multicast. IP multicast is a technology for efficiently sending the same content to multiple destinations. It is commonly used for distributing financial information and video streams, among other things.

A full list of IPv4 multicast assignments can be found at:
http://www.iana.org/assignments/multicast-addresses

That page indicates for 239 addresses: "Organization-Local Scope"

I don't know what means but perhaps something within your own network??

By the way, you may want to remove these extensions or at least disable them:

• Installl Converter Community Toolbar 3.21.0.1
• Searchme 2.4

You can do that on the Add-ons page. Either:

• Command+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, if in doubt, disable or if you think these snuck in with some freeware (video viewer/downloader/converter?), remove them.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Hope that helps.

HI,

Thanks for your help.  Neither of those extensions you mentioned are on my computer.

Hmm, they were listed in the "More System Details" next to your post.

In case they are self-hiding extensions, could you check again in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

After Firefox shuts down, a small dialog should appear. Click "Start in Safe Mode" (not Reset/Refresh).

Does the Add-ons page look any different?

Thanks again. I'll try it tomorrow and let you know how it goes. Really appreciate your help. Have a good night.