Drive error when connected internally but drive is fine if used as external drive

[Guest]

On my Win7-64 system I have a 3TB Hitachi drive which, when connected as an internal drive exhibits behaviour as described in http://www.tomshardware.com/answers/id-2278668/internal-storage-drive-stops-working-device-error-explorer-exe-error-valid-win32-application-error.html.
It will start out fine but after a while .exe files are no longer recognized and Windows Explorer will get seizures. I ran the extended test of WinDFT (Hitachi's drive test tool) and it pronounced the drive "healthy". Chkdsk, however, found errors that it was unable to fix.
I then removed the drive from the computer and inserted it into an external, USB connected "Toaster". I re-ran chkdsk and it had no problems fixing the drive. The drive will work fine as long as it is USB connected. When I try to insert it back into the computer, after a short time it will fail as it did before.
I replaced the cable, replaced the power supply, re-loaded the drive, re-loaded the operating system, ran memtest, - I tried pretty much anything other than replace the motherboard. (sadly no free SATA ports so I can't use a different port)
Any ideas what could be going on here? Do I need a bigger hammer to fix this?

 

[Boogieman_WD]

Hey TheAncient. You've basically done it all except try the drive internally with a different computer to see if the same thing happens. If you don't have access to another computer, then you could just disconnect another hard drive which you don't need running right now or an optical drive if you have one, to see if the problem is with the SATA port indeed, but as I said, it would be best to try it witn another PC. Also, run the tests again when you do try it with another PC/SATA port to see if you get the same results.

Hope that helps.
Boogieman_WD