Sorry if this is old news, but I learned something new after having had to reinstall Garmin onto my iPhone (I mucked around with some settings and somehow managed to hose the Garmin app on my phone)--at least one of those SID files is required for when selecting a destination via the Contacts book option; for grins, when I reinstalled Garmin on my iPhone, I did not install any of the four SID files (D2656xxxA.SID for External Point Addressing, D3157xxxA.SID for InstaSearch, D3406xxxA.SID for trafficTrends, and D3398xxxA.SID for Fast Routing) just to see if the Garmin (2.2) iPhone app really needs any/all of those SID files. Turns out that without the InstaSearch SID file, selecting destination via Contacts will not work (search screen will just show the spinning wheel and eventually cause the Garmin app to crash).

Given the above, whenever you're updating the maps, make sure you update the corresponding SID files appropriate for the map version you're looking to update/install...or at least make sure you have a valid InstaSearch SID file.