Most files have changed folder in the latest version - Alex emailed two versions for testing this error log issue and they worked perfectly well, both of them, so this log issue will be fixed in the next version of Dragmath.

Folder classes does not exist in the latest version so you will need to change codebase to

$urlforcodebase = $CFG->wwwroot.'/lib/DragMath/applet';

Clean cache/browser history before testing...

Attached the file structure of 0.7.7.1 and chkjre version of 0.7.8.1