well, I know this is old. but I run into the same problem.
And here is the solution :
1. The documentation is right, put *.mll in the bin\plug-ins folder and *.mel in scripts\startup
2. But, have a look at this
http://www.truevision3d.com/forums/tv3d_sdk_65/maya_plugin_problem-t10193.0.html%3Bmsg71411 : you must copy the TV3D65.dll from C:\Program Files\TV3D SDK 6.5\sdk\cppdll to Windows\System32, or maybe just the folder where environment variabel path point to it.
this is my first post
it simple, but I hope this will be helpful to newbie out there.
I don't know about you, but for me, 3D modeling is very hard to be tamed!
Gosh!