I never encrypted the drive and prior to this problem it worked normally with four different computers. After the problem started none of them was able to access the drive. All had the same issues. One has Windows Vista and the other three have Windows 7.
As I said in the original post, I took out the drive from the enclosure and attached it directly to my computer in an open SATA port and the drive did not work and not even appeared in the BIOS setup screens.
I have not tried formatting it since it causes the computer to become unstable and some applications hang until I disconnect the drive. Looking to see if I can recover a few things from it but I don't think I will be able to do so. The really important things (pictures and videos from a trip) were fortunately backed up elsewhere and were not lost.
It could be encrypted with Windows. Have you considered just formatting it, and seeing if it works then? Or, unmount it("eject" it), and then run something like recuva to see if you can pull some files from it.
It is VERY possible that the LaCie enclosure encrypts the drive using a proprietary method. Some of the other enclosures do it. -- These opinions are strictly my own. However, if you really want them, we can negotiate.