Your Query might look OK in the code, but does it actually send out correctly? For example, does it send a the Query header, then a Pong, then the remainder of the Query? (because you're not controlling the outgoing flow).

What you should do, is install a number of Gnutella clients on your own system, then connect to them with your Gnutella client (make sure, each other Gnutella client uses a different port, of course). Once you've done that, send out the query and see how the other clients respond (ie., any error messages etc. BearShare provides fairly decent info on that, so does GTK-gnutella).