I think I agree with you, it looks like you can't use the Neq operator against multiline types. I've used it many times on simple text fields without any problem.
I've just created a new column and it doesn't work with U2U's caml builder.. I'm guessing it just doesn't like a text comparison with the multiline string, not sure how this is stored in the object model, possible a string array in which case I can udnerstand the comparison not working. I just tried and you can't use Equal either.. You can use begins with though!
Paul.
www.myfatblog.co.ukMCTS: WSS 3.0
MCTS: MOSS 2007