Trouble running build command: wrong type argument: stringp, nil

Hello,

I've been trying to run an ant build file using JDEE and I've been  
repeatedly getting this error message:

-*- mode: compilation; default-directory: "./" -*-
Compilation started at Mon Dec 10 11:49:46

ant -Dant.home="/usr/share/ant" -buildfile '/home/user/Projects/ 
frontend/textsearch/build.xml' -emacs

Wrong type argument: stringp, nil

I've setup a project that points to the ant build file and I run build  
with C-c C-v C-b and it prints out that error. I'm using Emacs 22.1.1  
on Ubuntu with the latest version of JDEE.

I also enabled the debugger and got this output:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
   start-process("compilation" #<buffer *compilation*> "/usr/bin/zsh"  
"-c" "ant -Dant.home=\"/usr/share/ant\" -buildfile '/home/user/ 
Projects/frontend/textsearch/build.xml' -emacs  ")
   start-process-shell-command("compilation" #<buffer *compilation*>  
"ant -Dant.home=\"/usr/share/ant\" -buildfile '/home/user/Projects/ 
frontend/textsearch/build.xml' -emacs  ")
   compilation-start("ant -Dant.home=\"/usr/share/ant\" -buildfile '/ 
home/user/Projects/frontend/textsearch/build.xml' -emacs  " nil nil nil)
   compile-internal("ant -Dant.home=\"/usr/share/ant\" -buildfile '/ 
home/user/Projects/frontend/textsearch/build.xml' -emacs  " "No more  
errors")
   jde-ant-build("/home/user/Projects/frontend/textsearch/build.xml"  
nil nil)
   call-interactively(jde-ant-build)
   jde-build()
   call-interactively(jde-build)

Any ideas?

Thanks in advance,
--
Matt Ronge