I've got two different USB flash drives which are formatted MS-DOS(FAT-16). When I plug each into my MacBook Pro (running MacOS 10.6 - Snow Leopard), they don't mount. I can see them using Disk Utility. When I run an Ubuntu VM inside of VMWare Fusion, Ubuntu has no trouble mounting these either.
I've tested with the drives plugged directly into the machine and plugged into a usb hub -- both give the same results.
Is there a setting I've inadvertently set which disables automounting? Is there an issue with mounting FAT-16 drives?