Create a new profile as a test to check if your current profile is causing the problems. See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

Profile Backup and Restore

• http://kb.mozillazine.org/Profile_backup
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Creating a new profile did not work, unfortunately. I have also tried reinstalling Firefox and inserting one of the old sessionstore.js files, edited and renamed, from the sessions folder from my original profile. That loaded correctly, but closing and reopening Firefox reverted to the old problem.

I've been playing around with profiles, reinstallation and sessionstore.js files for a day or two. It seems that whatever combination of these options I try, the problem reappears.

I've just had a thought: could the process of synching a new installation be causing the problem to propagate from the old installation to the new one? I'll give that a try by reinstalling and not synching - meanwhile any thoughts on anything else I can try would be very welcome.

Didn't quite follow the process described in my last paragraph above. I went back to my main system (I mentioned that I have Windows Vista dual-bootable on my original post) and disabled my extensions in turn. It transpires that three of them appear to cause the tab URLs to be dropped, leaving just the label 'New tab' and 'about:blank' in the address bar:

• Tile Tabs 11.5
• Tab Groups Manager 2011.11.28.1
• Web Developer 1.2.5

It would seem that all three are incompatible with Firefox 28.0, which is a pity as all three are useful. However, I need to try a few more things to convince myself that the problem is solved. Has anyone else experienced similar problems?

I have removed and reinstalled all three to make sure that the extensions themselves are not corrupted in some way. I have left them disabled, as they do cause the problem to reappear.

jdgale,

Has your problem been solved?

On a related note, the above extensions you have listed are indeed compatible. I'm using Nightly 31.0a1 on Ubuntu and they installed fine.

• https://addons.mozilla.org/en-US/firefox/addon/tile-tabs/?src=search
• https://addons.mozilla.org/en-US/firefox/addon/tabgroups-manager/?src=search
• https://addons.mozilla.org/en-US/firefox/addon/web-developer/?src=search

Hi Moses - I want to do a few more checks to confirm that I have found the cause of the problem, namely the three extensions I mentioned above. I am intrigued that you have not had the same problems with Ubuntu that I have had with Windows. I have OpenSUSE 13.1, so I want to see whether Firefox 28 behaves itself with these extensions on my version of Linux.

Thanks for the links; I had been using them to download and reinstall the extensions for Windows, but it is reassuring to know that you have used them as well. I had no problem installing them - it is the problem they seem to be causing that bugs me.

Incidentally, I have reported what I have found to Mozilla, but so far I haven't heard anything back.

jdgale,

The comments that you have sent through the Mozilla Crash Reporter show up when we look through the crash reports. I don't think I've ever received a comment back from Mozilla even before I started volunteering. I think the comments are used as feedback so developers cna understand more.

I'm back at square one - I am losing the unvisited URLs regardless of whether or not the extensions that I thought were causing the problem are enabled. Any suggestions as to where I go now?

To add to the mystery, I booted into my Linux installation and checked that it had updated to Firefox 28; it had. What I believed to be the offending extensions were installed and enabled. You will not be surprised that the tabs were being restored without any problem, destroying my claim for the three extensions being incompatible with Firefox 28.

I need to think again.

After a load of tinkering with repeated reinstallation of Firefox 28 and extensions on several installations (Windows Vista and OpenSUSE on two different machines) I have come to the conclusion that the problem occurs with this particular version of Firefox and the combination of extensions that I am using. It appears that if I remove all extensions the problem goes away - but the extensions must be removed, not merely disabled; it seems that their presence alone is enough to cause the problem.

Rather than continue to beat on the issue with my limited expertise, I have installed a beta version of Firefox 29 and installed all my extensions. The problem has not - so far - manifested itself. So I have to conclude that there appears to be a problem with Firefox 28, but it seems to be buried deeper than I can explore. If anyone wishes to dig into this further I can provide a list of the extensions that I have installed, but as far as I can tell noone else has experienced this problem. From a practical point of view I don't think this is worth pursuing any more - I just hope that in progressing to its final release Firefox 29 doesn't pick up whatever it is in Firefox 28 that has been giving me grief.

Hi jdgale,

Glad you had that working. Quick question:

• You installed ALL your extensions that you had from your previous 28 installation? And it works fine?
• I was going to say that only ONE of your extensions was causing the problem

Hi Moses,

Correct; I have installed and enabled all extensions and for several days now the tabs have been restored each time I restart Firefox. I had tried removing the extensions one at a time to try to pin down which one(s) might be causing the problem. Initially I thought that I had found three (see my post of 10 April above):

   Tile Tabs 11.5
   Tab Groups Manager 2011.11.28.1
   Web Developer 1.2.5  

However, you pointed out that they were compatible with Firefox 28 so I pursued other lines of enquiry which suggested that it might be a combination of extensions that caused the problem. As I said in my previous post, I do not have the expertise (or, to be honest, the time) to go further, which is why I have opted for the easy option of a 29 beta.

jdgale:

I understand not having the time to do that. However, 29 is right around the corner and will be put in the release channel on the 29th, so let's hope the issue doesn't carry over for you.

P.S. I had originally chosen your last reply as the solution as you migrated over to 29 but looks like you've taken it off. I'll be marking your last reply as the solution so we can get it out of the queue.