proc_open() problems

I've written a script that uses proc_open() to call and external program and capture it's output. My script works fine as long as I call/use it in the directory where it resides. But if I try to include() it in a script that resides in another folder proc_open() return an exit value of 255. I can't access the external program. What am I missing? Some file perms? I did a "chown -R apache *" from the top directory but that didn't help ... I'm using the php.ini-recommended file. Is there some setting in there I should change? Jc