I've just moved an EE v2.7.2 site to a new server, following the EE-docs thoroughly. Verified all paths and file/folder permissions.
Everything works well until i try to edit or publish an entry, getting the error message below.
To get a WYSIWYG editor i'm using Expresso field types for my 'summary' and 'body' fields, and as soon I write or edit in one of these fields it is not possible to submit without the error. If I use only the other non-Expresso fields there is no error message.
Everything was working perfectly on the previous server.