Almost empty .htaccess file causing 500 error response
I guess your .htaccess file is in DOS format and it needs to be in Unix format.
Do not save .htaccess in UTF-8 encoding and convert it to a regular ansi. In my case server don't like this BOM thing at the very begining of the file.
Notepad++ is cool. Try this:
Edit --> EOL conversion --> Convert to UNIX format