I kept getting logjammed checking my personal e-mail at work, so I made separate profiles in Thunderbird for each. However, every once in a while, I want to open both at once to monitor incoming e-mail from both my personal and work accounts. In order to do this, you need to provide the -no-remote switch to Thunderbird.
I updated my launcher like this:
 icedove -no-remote -ProfileManager %u