Remove map data (set) from Garmin Nuvi 350 via MapSource

I got a hold of the MapSource City Navigator Europe from a friend and
installed it onty my desktop so I could play around with it, create
way points, etc. for evaluation purposes. I'm planning a trip to
Europe later this year and wanted to know what to expect when I
purchase the software, especially considering the $300 price tag it
carries.

Long story short; I ended up creating a map set and then transfering
it to my Nuvi 350. Now when I boot up my GPS it complains and says,
"Can't unlock maps." The existing base maps are still fine and after
I click the "ok" dialog the unit works normally. Now for the life of
me I can't figure out how to get the map sets back off my GPS so I
stop getting the dialog when I boot it.

I've read a couple notes about putting the POI database back onto the
GPS, but this was in reference to a different model (non-Nuvi). I was
hoping someone in this group could point me in the right direction?