Okay you need an extra installation disk for GARMAP AFRICA SERIES 2008 SOUTHERN AFRICA STREETMAPS, MARCH EDITION to make the SD card work with MapSource.
Can buy them from Chris Boltman, R100.
Corné Kloppers
http://www.bikepics.com/members/pantsula/07f650gs/
0849130391
ckloppers@gmail.com