I guess its the same problem i'm having then. Sometimes (or rarely) i have trouble getting into first. If i just slam it into reverse i get the clunk sound. Sometimes i can't shift into 2nd gear forcing me to slam it into gear.
Heres my old thread i posted in the online mechanic forum.
zerothread?id=143367
I bought a new slave cylinder, butI haven't had the time check what s13sr20chris suggested. If you try it, post back here please.
Also start a thread in the NIssan Online Mechanics forum too. You'll probably get more help there.