Problems with html2ps and php4

Hi Has anyone used the html2ps script with PHP4. I have it working on php3 but when I try to use it with php4 on a different machine it refuses to write anything to the postscript file instead it gives me an empty file. I have checked all my permissions etc to the neccesary directories and they seem ok, plus if I run html2ps outside of PHP4 everything works ok, so either I'm missing something or it seems to be the way it is interacting with php4. I am using the exec function in php to shell out to the program with full pathnames to the files, I have also tried using system() and passthru() with the same results. I have tried the debug option with html2ps but that tells me everyting is ok! Any help would be appreciated. thanks Nick Steele