Server errors (500), frequent problem with many Prestashop installations

[striky]

I recently went live with my shop, but there are some problems that keep popping up. Some of my customers have reported that they got a 500 server error when confirming their payment. I've also experienced the same in admin.
Browsing this forum, this 500 server error seems to be a problem for a lot of users. Some say that their problem went away after doing chmod 755 or 777 to the folders or files. I've tried this, and while it seems to work in some cases, next day I get a new error report from a user who has experienced a 500 server error.

What is causing this? I've worked on a lot of different web shop systems and php in general, but have never experienced this kind of errors before?

I think it would be in the interest of both the Prestashop developers and the users that this question gets a real explanation.

[TropischBruin]

To me a 500-error is server related, not PS.

What are your server-logs telling you?

[striky]

I don't have access to the error logs, but I typically get this message (which also has been reported by several users on this forum)

Server error!

The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: validation.php

If you think this is a server error, please contact the webmaster.

Error 500

[TropischBruin]

Server error!

The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: validation.php

If you think this is a server error, please contact the webmaster.

Error 500

You still need to contact you hoster to see what the logs are saying.
If your server is configured wrong the PS scripts will generate these errors wich look like they are caused by PS but actualy are there because of a wrong server-setup.