Do you mean that two windows open when you start Firefox or do you see two Firefox processes in the Windows Task Manager? In case of the latter, is one of them a plugin-container process or are both Firefox processes?

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

The Firefox window appears twice on the desktop, and task manager lists it twice.

Another problem appeared at the same time - the window allowing me to select a profile does not appear. I have many tabs open in each profile, and possibly I have exceeded a max value.

I can open the window to select a profile by using the windows logo key and R, and then run firefox.exe -p.

Sorry about the late reply, but I thought I would receive an email notification. Possibly, I didn't set things up for email notifications. Jim

Found the problem! I had my options set to show my windows and tabs from last time. I had so many open tabs, two instances were needed to include all of them.

I'm still reviewing and deleting these tabs. Once I only have a few open, I should see the profile selector window by default. Jim