I also have this problem as was just about to make a thread when I saw this one.
I did everything Senor Coolguy has tried, plus I created a new End, tested it worked, then pasted the files into the tekkit world_the_end folder. This still gave me an obsidian platform in the middle of nowhere.
I then opened the world file in MCedit, and I believe I have found the problem.
As you can see, the end has spawned correctly, but when entering the End it creates a new set of chunks away from the original and places the platform there.
The coordinates when on that platform are x= -950, y= 40, z= 386, and I was under the impression that the platform always spawns at 0,72,0.
There must be something conflicting with the spawn point to put it there.