Updated OS, Now External HD Won't Mount

This has been so frustrating. Just this morning, I transferred data off of my iMac G4 1Ghz to my external 1TB WD Elements external HD. I updated the OS on the iMac from 10.3 to 10.4, made all the necessary Software Updates to get the computer all caught up to 10.4.11 and now it won't recognize the external harddrive. My Intel Macbook still boots the harddrive right up, so I know the hard drive is operative. I'm wondering if there is some sort of USB driver issue with the updated software? Any thoughts? [I'm attempting to ferry user files to the iMac to clean up the Macbook]

Forgot one thing, Disk Utility does recognize the drive.

Thanks in advanced for any support.

Try running Repair Permissions on your internal and external hard drive as Disk Utility recognises the external.

Thank you for the quick reply. Although Disk Utility recognizes the drive and I can "get information" about it, Repair Permissions is not an available selection.

Thanks again for the help!