hard to know exactly where to jump in.
did you use Activity Monitor to search for any sign of procs with a relevant name (presumably containing 'garmin' somewhere therein)?
Can you open that plugin's installer (either with Installer.app or Pacifist) and give us some idea of what it installed and where? [with Installer.app we can use command-i to (hopefully) see the items... but perhaps Pacifist is better. Else, give me a path to that package and we can try terminal (either
lsbom or
xar).]
PS: since i don't have that Garmin goober myself, i'm just winging it here.
]
