404 Page coming up when trying to change products or edit in Define Editor

[Heresy Miniatures]

www.heresyminiatures.com/shop

When I'm in Admin and trying to edit using Define Pages Editor, or edit a product to change price or quantity, suddenly I am getting the 404 page when i attempt to save changes or preview a product after making a change.
Thing is, nothing is coming up in the Logs folder so i don't know what the error is. I did try to install the ZCA Bootstrap template a few weeks ago which caused some problems but as far as I know I deleted all the ZCAB files and it should all be pure original responsive template stuff in there now...
Where else can I look to find out what the error is? Or should I upload a fresh set of files? The site is live

[mc12345678]

There should be server logs generated when the issue occurs. May need to speak with your host to either obtain them or identify where they are located.