[exim] Help debugging pipe transport

I have a pipe transport set up to run a specific script, but when an
e-mail gets routed to the transport, I get the following error message:

2005-04-14 09:07:38 1DM50L-0005dc-S3 **
localpart@??? R=test_router T=test_transport:
Child process of test_transport transport returned 127 (could mean
unable to exec or command does not exist) from
command: /usr/local/bin/testScript

I've checked everything I could think of, but I can't figure out why the
script won't execute. The permissions are 775. How can I get more
debugging information to find out why it refuses to execute?

Thanks,

Jason Martens