phpbb3 - unable to install

[#1]

have previously successfully hosted a phpBB forum on my old account, but for some reason, this time I am having no joy in getting it to run, I have uploaded and reupload and checked permissions each time but keep getting the same message each time, has anyone else had issues getting phpbb3 to run it's install process?
this is the error I am met with each time
Server error!
The server encountered an internal error and was unable to complete your request.
Error message:
Premature end of script headers: index.php
If you think this is a server error, please contact the webmaster.
Error 500

[#2]

OK, I think I have sussed it almost as soon as I posted.
This may be benefit to other who are trying to install...
I could not get the site to ruun unless I enable the executable permissions on the files (I thought PHP did not use the executable permission)
I hope this saves someone some headscratching time

[#3]

You might find reading the CGI Platform PHP Upgrade FAQ useful. That covers the CGI upgrade to PHP 5 in March last year and provides links to scripts which make it easier to get applications to install and run on the new platform.