Can’t access my theme files for editing…

I am only able to access the main .css file in my theme today. None of the php files will load when clicked. Nor will either of the other 2 CSS files.

When I click to load another file, the page refreshes and the url changes as if it has loaded, but the actual editor content remains from the original CSS file.

Just last night I was modifying all of these files with no problems.

I have tried logging in from both FF and IE. Same result.

For the 1 file I can access, I am able to change and save as normal.

Any ideas what is going wrong?

Thank you.