Links from Mail and other apps don't go to open copy of Firefox but attempt to open a second copy, so I get "A copy of Firefox is already open," FF 22, OS10.8.4
Links from within Firefox windows open new tab, but links within Mail, MSWord, and other apps attempt to open another copy of Firefox, and I get the "Close Firefox: A copy of Firefox is already open. Only one copy of Firefox can be open at a time." This just started happening less than a week ago. I don't know when FF updated to version 22.0.
ప్రత్యుత్తరాలన్నీ (3)
This can happen if Firefox has been started with the -no-remote command line switch, but that may not be likely on Mac.
My problem seems to be fixed--I cannot reproduce it now, though it had been consistently happening for the past 3-4 days. The suggestions above do not seem to apply in any case: I do not want to open another instance of Firefox but simply to connect with the one that is already running; and I do not seem to have a .parentlock file.
If the problem returns, I'll be back. Meanwhile, thanks for the suggestions.
Did you close and restart Firefox or reboot the computer previously?