Usually the original publisher would provide an uninstaller for its plugin but, if there isn't an official Blackberry uninstaller, you probably can just delete the file (from the path you mentioned). If you are concerned that it might be needed for any other purpose, you could move it out to a completely unrelated folder first as a test and see whether that has any adverse effect on Firefox.

As for detailed instructions, I'm a Windows person, so I'm not sure how best to get to that specific path you got from the about:plugins page using Finder. Can you track it down?

As stated in my question the path is: Path: /Library/Internet Plug-Ins/FirefoxAPI However "?firefoxAPI" is not listed in the plug-ins list. I restate: I have spoken to Blackberry, my telecom carrier & to Apple; Apple says this plug-in is in the Firefox app & not "on" the Mac.

josephwm said

However "?firefoxAPI" is not listed in the plug-ins list.

What plugin list are you checking? Do you mean Firefox's Add-ons page or is this a system-level or Safari list?

If you mean Firefox's Add-ons page, don't worry about the difference. Plugin file names do not always match the names on the Add-ons page. If the about:plugins page says that is the actual plugin file corresponding with Blackberry World, then that is the best information available. If you can open that path in Finder, try removing the file specified on the about:plugins page.