I'm glad I saw this thread.
I've been having a problem blanking null value attributes since upgrading autocad. In 2005 I could use find and then replace with nothing.
Since upgrading to 2009 you can't replace with nothing, a value has to be entered in the "replace with" box.
but
(defun c:nv ()(nullvalues "-999.00" ""))
works a treat thanks Lee and GDF!