That's a strange behavior on the part of Comcast. Could you try the same page in Firefox's Safe Mode? That's a standard diagnostic tool to bypass interference by extensions (and some custom settings). More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

Any difference?

Speaking of extensions, "Updater by SweetPacks" sounds like software most users do not want on their systems. You can disable and likely remove this extension on the following page:

orange Firefox button (or Tools menu) > Add-ons > Extensions category

If you get a link above the extension to restart Firefox, click that to complete the action.

You might also need to check the Windows 8 Control panel, Programs and Features to uninstall other SweetPacks-related software.

Thanks for the help. In safe mode Comcast mail works as it should. I'll have to find which extension was causing the problem