Vagabond: Maybe you need to specify the same directory as all the game's discs. Go to the "Drives" tab in the edit profile window and checkmark "Additional automatically mount all available CDs."
ChaunceyK: Well, this didn't do it. And I uh...let's just say I did something stupid & lost my saved games. So Stonebro may have the correct answer (I found something at SierraHelp.com), but I won't know until I get to the end of the game again. :-(
Looking at a GOG configuration, maybe you can emulate this:
imgmount F "UAKM1.GOG" -t iso
imgmount G "UAKM2.GOG" -t iso
imgmount H "UAKM3.GOG" -t iso
imgmount I "UAKM4.GOG" -t iso