Problem with the mass multiple files upload

Hi All , I got into trouble when try to use multiple files upload in PHP4. I use '[]' after field name as usual like this. <form action="upload.php" method="post" enctype="multipart/form-data"> 1.<input name="userfile[]" type="file"><br> 2.<input name="userfile[]" type="file"><br> 3.<input name="userfile[]" type="file"><br> ..... 40.<input name="userfile[]" type="file"><br> <input type="submit" name="submit" value="Upload"> </form> And in "upload.php" is while loops to get the filename in an array and then copy to specify path. So, if I use the input box just 38 boxs and preee submit this seem to be no problem. But if I add more input box (at least just 1 box) to 39 boxs or 40 box or more. The error 500 internal server error is display from apache server (I tested on Windows ME and Linux -- Just display >38 boxs the error will occur when press the submit button (it can display but can't submit) , although I add just 1 file or nothing to upload) and in error log file is display like this : "Premature end of script headers:" I have no idea what to do so. Any answers are alway welcome. Thanks in your advance , -Chippy Ho-