tidy cuts half of the html-code

hi folks,

i have a problem by using tidy from a php-script like this:

$aufruf = "C:\\WINNT\\tidy.exe --tidy-mark no --indent yes --clean yes  
--logical-emphasis yes --write-back yes --error-file
".$path."mytidy.log  ".$path.$filename."";
if(!$tidy = popen($aufruf,"r")) //.......

the output-file seems to be cutted somewhere in the middle and the rest of  
the code is gone.
maybe a buffer-problem?

Greetings,

Joerg