is it possible to screw up a throwout bearing install?

[David Pertuz]

Coupla years ago my TOB is noisy and getting worse, so out comes the tranny
and I repalce it and the clutch. That was at 112k miles. Now I am at 165k
and -whirrr! - my TOB is starting to pipe up a bit again ?! I am not really
worried about it for now, but I am puzzled. What can one potentially do
wrong in an install? I mean, it's pretty simple...put TOB on shaft, grease
it up good, put clips on, etc. I sure don't want to have to drop the tranmy
again in another year or so just to replace that little $35 part.

david