The internal Hard disk eject spontaneously

No but maybe you need to reformat, check that it makes proper contact with the power and data plugs.

Was there a drive in that drive bay before also.

What is rhe rotational rate for that Samsung disk, 72000rpm or a 54000rpm? Reason I am asking is because I put a Samsung 1Tb 54000rpm in my #3 bay and it is doingthe sdame thing yours is doing. It is just a theory, but I can not see why that should make a difference. The !Tb (Hitachi) that came pre-installed with my MacPro is 72000rpm as is the 1Tb (again Hitachi) that I had in my old computer, Those are fine and no problems with them. But with the new 1Tb I got - trouble!

Green are fine, as long as they fit properly though sometimes their firmware for parking head, spin down etc has been more trouble on Mac Pro and OS X. Hear that about WD Green.

Rotation speed is not an issue. WD did use variable rpm in some of theirs.

And some external green drive cases have had trouble with TimeMachine and drive 'falling asleep' during backup operations.

I have half a dozen WD green not sure why Lion or what is wrong with these.

Like I said in ny post I am having the same problem! I have a Samsung 1Tb and I can not figure out why it keeps being dismounted for no reason. I considered the rotational rate but "The hatter" says that it is not an issue. But the problem remains, and that is the only real difference between any of the three 1 TB`s that I have in mine other than the other two are made by Hitachi. I have also installed that Samsung in my old G-5, and no troubles, But when I put it into my month old MacPro bing sooner or later it gets dismounted! I have an appointment at the local Apple store tomorrow, so I will ask their expert.

Updaye

I am waiting for them to call me as they had no experts avaikable at the store yesterday. They got my info and said they would call me.

Update. I talked to the Mac "expert" at my local Apple store and he arranged for pick-up. They came on the twenty third and picked it up, the computer was delivered twenty minutes ago and it seems ok now. They replace part number 661-5706 Which is listed as BOARD BACKPLANE W/BT. After getting it back, it seemed that my USB ports were not working, so I tried a Bluetooth mouse on it and after it connected I noticed that my USB keyboard was working, so I connected my regular USB mouse and that worked, so disconnected the Bluetooth mouse and everything seems fine now as I am writing this.

Seems that I was too fast! Just a few minutes ago the same old problem returned- the HD got dismounted by it self! Going to call my local Apple Store tomorrow.

Apple expert told me to take that Samsung HD back to where I got it because he said" there is something wrong with it" This is the seond Samsung HD I have had this problem with!

so? any news?

Sorry about forgetting about this, anyway I sent the computer to my local Apple repair and yup the disk would eject, so they told me that the other disks I had in it are 72000rpms and the Samsung was 54000rpms, so it would not work in my new computer, I could not for the life of me understand that logic and told them to take the computer and stick it where the sun does not shine, got the money I paid for it and bought a second hand Pro an older model, stuck all my hard disks in it, hit the start button, everything worked, the Samsung is still working!

It is very possible they were correct in what they were saying but after shelling out almost $5,000, I seriously was in no mood to hear that, but I am glad I ditched that Pro as I can not wait for the "trash cans" to come out, going to get me one.