Here's a screenshot:
Go to Solution.
Try the Firefox SafeMode to see how it works there.
A troubleshooting mode, which disables most Add-ons.
Troubleshoot Firefox issues using Firefox SafeMode
When in Safe Mode...
To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before using the Firefox shortcut (without the Shft key) to open it again.
If it is good in the Firefox SafeMode, your problem is probably caused by an extension, and you need to figure out which one.
When you figure out what is causing that, please let us know. It might help other user's who have that problem.
I found the culprit. It was indeed an extension i had (well the lastest version of this extension).
« Delicious extension 2.3.1 »
It is disabled now and i can finally see the content of my address bar.