Hi,
This is because the version of ACE (code highlighter) does not like IE8 (or IE 8 mode).
You can downgrade to a previous version of this plugin by replacing the contents of this folder “/SPJS/DFFS/ace/src-min-noconflict” with the files from a version before DFFS v4.4.3.37 – please note that the folder structure in older versions have the files directly under the “/ace” folder, but you must use the new folder structure.
Alexander