Seagate 4 TB partitioned volumes greyed out on MacBookPro (10.6.8)

My Macbook Pro (late 2007) OSX 10.6.8 is not reading a 4 TB Seagate external drive. 1 TB is partitioned for Carbon Copy Cloner and 3 TB contains my Music. I had issues yesterday with the Music volume appearing greyed out. After restarting via Startup Disk, the music volume appeared. I went a bit ahead of myself and tried rebooting through CCC. The system powered on with a ding, but I got this spinning grey circle and after 45 minutes I powered off by pressing the power button for 7-10 seconds.

When I powered on the Mac and plugged in the external drive, the finder wouldn't read it. Disk Utility shows both volumes greyed out, but the drive name/disk description is there. Both Verify Disk and Repair Disk say the volumes are fine. I tried switching USB cables, but nada.

Please help. I have been using this external drive for the last 3 years without a problem. It's a lifetime of music from LPs, 8-tracks, tapes and CDS.

Should I try Diskwarrior or TechToolPro? Any other tips?

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Can you mount it from disk utility? If you can't try from another mac.

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Wasn't reading from another Mac. But... I just turned it on after 24 hours and it's reading the music drive now!!! Fingers crossed until I back it up. Thanks a lot.

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