OS X is notorious for being more finicky about drives than OS 9. This is particularly true of SCSI disks (not the case here obviously). Might want to check your cabling and make sure you don't have a loose or pinched drive cable. Might also want to double check any jumpers on the drive to be sure they are making solid connections. But, the repeated seeks sound may be an indication of bad sectors on the drive that it is attempting to read. Have you tried running a disk utility and see what is says? You can use fsck from single user mode if you can't boot from something else to use Apple's utilities.

-Mike