Duplicate mount points on Mac
From your description, this seems like an issue with unmounting the drive not working properly or an unexpected restart of the system. When a drive is unmounted, the mount point under /Volumes/ should be gone. Otherwise Mac OS X would create a new mount point with suffixes like "-1", "-2" and so on since a name that's currently used cannot be replaced without a proper unmount.

There are a few things you could do to resolve this issue:


Ensure that you always eject the drive correctly.
Restart the system.
Remove the duplicate mount point in /Volumes
Apply the combo updater for Mac OS X 10.6.8 v1.1 and see if that helps.


References:
Remove the duplicate mount point in /Volumes
Drives in OS X appearing with '-1' appended to their names