User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322) Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; rv:1.7.3) Gecko/20041001 Firefox/0.10.1 I was using my Windows XP SP2 RTM system for about 3 hours straight and had no system errors. This is the first time Firefox has done this. I had closed all the windows out and then restarted Firefox. Then no window opens, instead I get the Profile Manager saying my Default Profile (I only use this one, because its only me on the computer) was already in use and that I was required to create an entire new one? Very strange. So I lost my bookmarks and settings too. Reproducible: Couldn't Reproduce Steps to Reproduce: 1. 2. 3. Toshiba M35 768 megs of RAM Windows XP Service Pack 2 PR of Firefox

I've seen something very similar to this on a co-worker's machine, so I wanted to see if the fix for her computer would help you... In my instance, the user had closed all of her firefox windows, but firefox had somehow remained open in the background. So when she re-opened firefox, it gave her the dialog for creating a new profile (since her original profile was in use). She's a normal user, so she created a new profile, but when it opened, all of her settings, bookmarks, etc. were gone so she called me to fix it. A check of the task manager showed two instances of firefox running, so I closed the visible instances of firefox, then I used task manager to kill the hidden instance. After firefox was totally closed, I edited the properties of the firefox shortcut on her desktop. I added a "-P" to the end of the Target line, then ran firefox from that shortcut. The "-P" forced firefox to pop up the profile dialog so that she could select her original profile. All of her settings, bookmarks, etc. were back and she was a happy camper. All I had to do after that was remove the "-P" from the shortcut and her system was back to normal.

I just encountered the same problem on my Fedora Core 3 installation. I have set options to display my Downloads window when files are being downloaded. I closed all instances of the browser window, but the Downloads window was still up. As a result, when I tried to launch a new Firefox browser window, Firefox complained that I had to create a new profile because the default profile was in use.

*** This bug has been marked as a duplicate of 239223 ***