when I enter thunderbird & at a terminal promt with thunderbird already running I get the message: /usr/lib/mozilla-thunderbird/mozilla-xremote-client: Error: Failed to send command: 500 command not parseable Browser doesn't understand command rather than the running thunderbird being bought to the front.
emerge info version of thunderbird and mozilla-launcher?
I often have this bug; it seems to me I get it when I emerge perl or XML things while TB is running; last time, applying My fix is: killall -9 thunderbird-bin then visit the profile folder: ~/.mozilla or ~/.mozilla-thunderbird or ~/.thunderbird depending on many factors, then find YOUR user profile ... then remove the lock file manually. To help, when you are in Mozilla directory, try find |grep lock but before removing the lock, first kill all instances of programm running on the UNIX user profile (I especially think about eventual X11 forward of SSH tunneling), and all process called thunderbird thunderbird-bin or mozilla-thunderbird(-bin).
I think you can mark this bug WORKSFORME or RESOLVED/INVALID. I really think it's a glitch in how the process creates the lock file ... glitch that will never be fixed.