I am having the same issue and it is bugging me bad, please let me know if you make any progress on this.
Thanks,
Mike
I think I found out how to fix the issue based on something I heard last night on a different forum. Someone mentioned that when they deleted the archive folder the NUVI built a new folder. Last night I deleted the GPX folder and all of the old caches went away. When I disconnected the NUVI and started it again it built a new GPX folder and to my amazement all my old caches were gone. There must have been a hidden file or something in that folder that retains the cache info. Or it is just magic! What ever happened I don't care because it seems to work. Thanks for your help.
I thought I had it fixed, but I was wrong! The situation is this. When you erase the GPX folder in the Nuvi it deletes all of the geocaches or at least it makes them invisable. As soon as you create a new GPX folder all of the old geocaches that must be stored in memory come back to view. The unit must be storeing this data in some other file. Now I need to find that folder and clear out that file. If you have any ideas let me know.