Something happened to my thunderbird profile: now every folder in the folder three pane on the left has the same standard yellow folder icon.
I mean that the special icons for INBOX, Trash etc. are missing.
I've tried to temporarily rename the profile folder, then restarting Thunderbird, now all the special icons are back again.
So the problem appear to be in the profile folder.
I don't want to delete my profile folder cause it contain all my emails.... :-(