The ckeditor.css file included with the module has an attribute of 'disc-type: none' assigned to the element li.sortableItem on line 119. I'm assuming it should be one of two things, but I'm not quite sure.
1. It should be list-style-type: none
2. It should be list-style-type: disc
These will have (obviously) different effects, but the rule did not exist in version 6.x-1.6, and appears first in 6.x-1.7 as 'disc-type: none' so it is difficult for me to say what was intended by this rule. I'm not sure where this rule would actually show up, but if I figure it out, I'll update this report.