Last night I needed to edit a few lines in a php file on one of my sites. I loaded up my ftp client and grabbed a copy of the file onto my local machine.
Not paying attention I just double-clicked on the file and it opened up for editing. After changing a few lines I saved it and put it back on the server, overwriting the previous copy. That is when all hell broke loose!
My site started acting wonky and blank pages were showing up in some areas but not in others. That is when I looked a little closer at the file on my desktop and noticed the notepad icon.
I quickly opened the file in one of my code editors and fixed the problem.
The key point here is that unless you are using a Microsoft IDE product DO NOT use a Microsoft text editing program (Word, Wordpad, Notepad) to edit a php file. when those programs save a file they throw a bunch of non-standard characters in there that cause problems.