I just finished tracking down a similar problem (Blank screen on new install) for a colleague. I think chrishajer may be on to your problem with the key but not all linux installs allow php command lines and my httpd access and error logs gave no useful info.
My colleague had copied the WP secret BUT not the whole thing. He stopped on an escape string (”) which made php think the last single quote in the definition syntax was part of the key. This made the entire rest of the file part of the text in the definition instead of letting the php interpreter at it. For example:
You can see in the first example that the escape character “” is what breaks the rest of the file for php. If your WP key is ending with “” (right before the single quote) then I would try deleting that character in both places and see if that does the trick.