wierd header output to pdf problems

hi guys i have having some wierd intermittant header output to pdf problems , i have made a system where i can make reports to pdf , either having the option to download or output to the screen and print , i am having some issues , where the download option is working fine , but when i try and header output to the screen i just get a blank screen sometime it loads acrobat's splash screen and thats it :\ here is the code header("Content-Type: application/pdf"); Header('Content-disposition: inline; filename=doc.pdf'); flush(); $this->convert(); where convert is the passthru output from htmldoc i have tried heaps of different things sometimes it works then i do something then it doesnt , i have tried this in the header header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); header("Cache-Control: no-store, no-cache, must-revalidate"); header("Cache-Control: post-check=0, pre-check=0", false); header("Pragma: no-cache"); i have also tried session_cache_limiter('nocache'); session_start(); as aparantly sessions cause error , i dont know what the problem is any ideas let me know thanks