On that other system, make sure, you also install Mr. Tech Toolkit.
Now, when I think about it, it may be a mix of both, which makes my add-ons working.
Normally, Mr. Tech always took care of incompatible add-ons, but with FF4, it didn't work by itself.
Then, I applied listed above edit and all worked.
I'd curious to find out, if it worked for you.