Basically this can mean anything, it is just the webserver indicating that something has gone wrong and that you should look in the webservers error log for more details.
If you have access to the errorlog, fine, if you donīt you are kind of blindfolded in a dark room when something goes wrong and you need to trace down the error. Personally, since I am a coder, I really canīt see myself using a webhost that doesnīt provide me with access to the webservers errorlog but I know this is quite common.
If you are in the situation where you donīt have access to webservers errorlog you could try and upload this script (provided by courtesy of LoneOwl) to your webservers cgi-bin directory and execute it. Make sure you have the chmod settings right!
Anyway, the message in the errorlog should give you a pointer of what is wrong and how to fix the problem. If not, the steps mentioned in the "Premature end of script headers"-section can be applied to this problem as well.
If the problem still canīt be solved, it might be a problem with the end of line character. This is often the case if you are running on a Linux server (at home maybe?) and use your Windows machine to edit and upload the files to the server from.
In particular, Apache on Red Hat has been known to be complaining even if the files are being uploaded in ASCII mode but this can be remedied by adding "-w" at the end of the shebang line like so:
Another way to handle the situation is to use a texteditor where you can specify the target operating system when saving the file. The Unix file format should then be used.
If you still canīt figure out why you receive this message post a message in the forum, stating that you have read this document and explain what measures you have taken thus far to pinpoint the problem.