I understand that the solution I'm about to state sounds incredulous, unlikely, doubtful, but here goes.
Replace the power supply (the wall wort power brick).
Yes I know the old one seems to work, powers the lights, etc. But really. Replace it.
My Vantec Hard Drive Dock used to work then after not using it for a few months I tried it again and it wouldn't work. Well it did work for 2.5" drives but not for 3.5" drives. I think that the smaller drives don't need as much current.
The new power brick was really an old one that had the same specs (12V 2000mA) but looked a little beefier. The output plug was the same. (Are manufacturers standardizing the output plugs based on voltage now? It seems so.)
So dig in that box of old components (you save all your old power bricks, right?) and give that a try.
If you don't have another power brick available then try a 2.5" drive in the dock and see if that works (as a test).
I concur with you. Having had a hard drive that stopped working, I sent it back under warrany. It was returned to me saying that one of the voltages from the power brick was too low to keep the disk working properly. The power brick was able to keep the lights working. The new power brick worked for many year after that until evenually the disk itself failed. So your suggestion is a good one.
Holy Cow! This actually worked for me! I was about to scrap the drive and buy a new one, but this actually got me going again, now I just need to restore my data, but the disk was unusable until this solution!!
Here was the error message:
"POSIX reports: The operation couldn’t be completed. Cannot allocate memory"
I solved in this way using Disk Utility:
- I partitioned in 2, one extended/journaled and one fat-dos
- I formatted as usual
Maybe a lucky shot, maybe not.