Just downloaded the new Tor browser bundle on my MACBOOK Pro and I get a message that reads "a copy of firefox is already running. Only one copy allowed at a time." Any suggestions for newbie, like myself?
Although it is not a "true Linux way", you could also force kill Firefox processes through the
"System Monitor" application, which is a part of Mac OS X system
It sounds like you've opened the .dmg and are trying to run the program before copying it out.
Drag 'TorBrowser' on to your desktop (or a temp folder) and try to execute it again.
Verify, via the terminal command
ps aux | grep firefox, that no previous Firefox process was abnormally stopped and kept in 'ghost' status.
If it's the case, kill the process via
kill -9 <id> or reboot the machine and then verify again, via terminal command
ps aux, that no Firefox process is still running.