[BaseCamp] Imported track data doesn't save

[Bill]

Recently I have been importing some sets of tracks into BaseCamp, they import no problem, show up in 'On My Computer - My Collection Briefcase".  I can show them on the map, view the detailed data list, basically do what I want with them.
However, when I import another set of tracks into BaseCamp and that appears to work fine except it replaces the previously imported track.I have made new folders, moved the tracks I have into that folder,, checked that they are there, but when I import the next set of tracks the previous gone from it's folder.
How do I get BaseCamp to save the tracks I import?
Bill PuckettShawnee, OK