Error 500 on checkout success page

Hi,
I have had to move a shops URL, and basically copied everything over from a 1.3.6 cart. So, I decided it would be a good idea to update the cart at the same time to 1.3.7 All seemed to go well, except when i purchase an item, i go through the appropriate stages and all is as it should be until the final 'success page'.

Instead of the page i get an error '500 Internal server error', I checked the error logs on the server and they are not showing anything up for concern related to this problem. I just don't know what else to try, i have checked the pages that i think are concerned with the checkout and success process, and checked with the version from 1.3.7 and they are exact.

have checked the configure.php files both in admin and includes, and can find nothing wrong with either of those, settings wise.

Please help if you can, many thanks.

Updated information, I found an error in the errorlog - it doesn't mean a lot to me suffice to say that I guess one of the PHP files is corrupt in some way, if anyone could point me in the right direction that would be great, here is the full error as reported in the log

[Mon Mar 05 23:09:05 2007] [error] [client 84.12.198.34] malformed header from script. Bad header=/home/pauls/dead.letter... Sav: php-script, referer: http://www.schneider-cabinets.co.uk/index.php?main_page=checkout_confirmation

Also i get the 'secure and non-secure items, do you want to display them' message warning - not sure if this is relevant at all?

Haha well this is a one way conversation isn't it, however:

I have found the solution!
The error that was being thrown (shown from the server logs), sent me towards UNIX dead.letter command, and ths is used by LINUX or UNIX servers when an email address is corrupted, this was the big clue!

The fix I found was that one of the email addresses i had added in the 'Send copy of order confirmation emails' part of the email section was incorrectly formatted. In fact I had inadvertantly left the < > around the single email address, this in fact was the UNIX error being thrown up on the servers error log.

I hope this might be of help to someone in the future, thanks.

Thanks for posting the update on the solution to this issue ... this is always a help to others to have both problems, symptoms and solutions ... even when you find the solution yourself ... :smile:

I had that problem also.

You get: > [Fri Oct 23 08:40:38 2009] [error] [client xx.XXX.xx.XXX] malformed header from script. Bad header=/home/SITE/dead.letter..: php-script, referer: http://www.SITE.nl/index.php?main_page=checkout_confirmation

[Fri Oct 23 08:41:28 2009] [error] [client XX.xxx.XX.xxx] malformed header from script. Bad header=/home/SITE/dead.letter..

It seems if you fill in a not working e-mail address you will get this error.

Nothing to do with ZC.