The latest Communicator plug-in from Garmin and USB drivers are installed. Garmin's Communicator Web page says all is OK.
The Geocaching.com function "Send to my GPS" (a Garmin) doesn't work with Firefox 13.0.1.
It always says "The plug-in was not unlocked successfully".
Have tested with both Windows Vista and Win7, same problem, but IE9 and Google Chrome both work fine, so the problem is only with FF.
How can this be solved?