Error message panel on desktop when I launch Firefox

Update: problem now occurs in all 3 user accounts, but not every single time!

I'm getting this error also and, while I don't know much about how to interpret the error message, I do know that one of the extensions I use, Tab Mix Plus, was just updated in the last few days; since the problem just started happening for me today, Tab Mix Plus would seem to be an obvious candidate for the list of suspects.

However, I just discovered that another extension I use, Session Manager, was also updated less than a week ago. And it seems a more plausible suspect because the error message is showing up before I even get the Session Manager window that lets me choose which (if any) previous session to restore. Do you happen to use Session Manager? The version I've got installed, 0.8.0.1, was an update of 18 April 2013.

Hi, many thanks for the response.

I don't use either of the add-ons you mention, I do use colourful tabs amongst many others.

The major updates I can remember around the time the problem started were Firefox itself, Shockwave, Realplayer download and Java.

After some investigation, including communicating with the author of Session Manager, I no longer suspect those add-ons either. The author of Session Manager, who could make much more sense out of the error message itself than I can, said that he'd reinstall Firefox if he were getting that message. I haven't thought through how much hassle reinstalling Firefox would be (would I have to make a record of all the add-ons and extensions I use and then reinstall those after reinstalling Firefox?), so I'm just suffering with the occasional error message for the moment.

I know what you mean. Uninstalling Firefox (before re-installing) gives the option of saving settings, worth a try, but probably won't solve the problem because the problem is probably somewhere in the settings.

I've done full re-instals in the past & it is time consuming; so, like you, I'm just putting up with the problem at the moment.

If you do re-instal remember to back-up your bookmarks first.

Thank for the thoughts. Regarding backing up bookmarks, I use an add-on called Xmarks (formerly known as Foxmarks) that automatically backs up my bookmarks each time I exit Firefox and it synchronizes my bookmarks across multiple computers and browsers too. Worth a look if you haven't tried it.

I use Colorful Tabs too, and this error started occurring (intermittently) after one of the Colorful Tabs updates. After receiving an update yesterday (I think), the error message now appears TWICE before the browser opens.

While I'm quite fond of Colorful Tabs, I'm less fond of the error so I'm going to disable to plugin and see what happens.

I have had the issue of two error messages (if you look carefully the two messages are not the same) after the latest colorful tabs update - it does now look very likely that this add-on is the source of the issue. I have removed it and like you will now keep an eye on what happens. Incidentally, I did try an uninstal and reinstal of colorful tabs and the problem immediately reappeared. Another oddity is that I have three user accounts on my pc, only one of those accounts had colorful tabs installed (all use Firefox), but the error message also appeared on the other user accounts. Very strange. It's a shame, colorful tabs is (was!) a nice add-on.

Disabling ColorfulTabs didn't stop the problem for me so I've just removed it completely. Since the problem doesn't happen on every start of Firefox, I'll have to see over the course of many starts whether the problem has now gone away.

Well, that didn't take long. I've already had an occurrence of the problem even though ColorfulTabs is now completely removed.