Editing in 2.7 Internal Server Error 500

So whenever I want to edit a post, or change the status of a comment, I do my work, go to action it and end up staring at a white screen with the following words on it:

Error 500 – Internal server error

An internal server error has occured!
Please try again later.

Which is conveniently non-descript enough for me to know what it means. I had to reinstall all parts of the site again when I upgraded to 2.7 and put the plugins back in. But this is a recurring problem since the upgrade and I’m buggered if I know what’s up.

I’m at https://www.mrxstitch.com if you’re interested.

Thanks for your help!