I'm trying to access some files for a client on a Western Digital external firewire/USB drive on my MacBook Pro. The drive will not mount in Finder. The upper level drive shows up in Disk Utility, but the partition of the disk I would like to mount (the only partition on the drive) is greyed out. I know that it's formatted for a Mac and has been accessed recently. In Disk Utility, when trying to mount or eject, the an error comes up saying to use first aid. Verify and Repair Disk don't change anything though. Any thoughts? Thanks.