You can make a backup copy of the sessionstore.js and sessionstore.bak files to be sure.

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

Were you using a custom theme or tab related extensions?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

None of what you said makes sense regarding the issue I am having. The problem, I have now found out after doing a little internet research, is that Firefox 29 is basically a pile of garbage. If you have more than a few tabs opened it causes your pinned tabs to "hide" which is complete nuisance. I guess I shouldn't have expected a solution from the people that are actually causing the problem. Silly me.

Do you happen to have an extension called "ColorfulTabs 23.1"? I had the exact same problem as you and noticed the pinned tabs start disappearing once you get beyond 6 ish normal tabs. If you do, disable it and it should be fine.　Otherwise check if you have any extension / add-on that might affect how the tabs look. Disable them all and check if it works then.

I had the same problem. Somehow (no clue how it happened) they all reappeared. However, I can't move any of my pinned tabs to a different spot. It's like they are 'locked' in their current positions forever...which isn't desirable..  ??

I had the same problem and found the solution. Apparently, firefox29 installs as add-on GlassMyFox. Once you disable it, pins appear as usual, though with this new tab look/style.

Unfortunately, that doesn't seem to be the case for me. I don't have GlassMyFox installed on mine, but it IS an add-on that I COULD install if I desired it. Perhaps you got that add-on installed on your Firefox some way besides just through the Firefox 29 update/upgrade that we just updated to. I can, like I said, install the GlassMyFox if I go to the add-ons and choose to, but it is not currently installed on mine....so it's some other issue causing mine to not allow me to move any of my pinned tabs.

Another issue I've seen with my pinned tabs is regarding my very first pinned tab (the one on the far left). I have it set as my Outlook/email tab. However, when I click on it, it doesn't open up there. It opens up an Outlook/email tab over on the right side with my "normal" tabs. And every time i click that pinned tab, it just keeps opening more and more Outlook tabs over on the righthand side with all my normal tabs. It WILL NOT open up that Outlook tab over on the far left side where it is pinned. All the other pinned tabs seem to open up in their correct pinned locations, but the very first one (the Outlook/email one) will not. So, basically, that very first pinned tab is behaving the same as just clicking on one of my bookmarks. When I click it, it just opens up another tab over in the normal tab area.

Yes, your issue sounds more complicated. I can only say that I have not installed GlassMyFox myself (and I am the only user of the desktop), so I assumed that the Fx update installed it. It did not work with pinned tabs and a theme I had/attempted to install after Fx29 update. Disabling that add-on worked for me. Hope, someone will find a solution for you. Best wishes.

I found that after Firefox v29, a LOT of my settings and add-ons were changed / reset. Try this; Start Firefox in Safe Mode
While you are in safe mode;
Firefox Options > Advanced > General.
Look for and turn off Use Hardware Acceleration. Check your setting. Then restart.