External drives not showing up in catalogue

Hi all.

Starting up Lightroom today I notice that I can't see any of the external drives that are mounted in the Folders list. There are 4-5 of them that I use with Lightroom, and usually they show up when I mount them. The drives themselves are connected by FireWire and mounted (ie. show up on Mac desktop etc). They just don't show in the folder list at all. Any ideas?

Thanks –– Ian.