I don't see a demo page for the EditorBodyStyle property on your website, so I can't give you steps to reproduce on one of your demos, but this is how I'm able to replicate in Firefox 5, Safari 5.05 and Chome 12.
1) set the EditorBodyStyle property to the following string "font-family:'Comic Sans MS';font-size:14pt;"
2) Load the CuteEditor and start typing. The first line looks fine. Comic Sans MS with font size 14pt is applied to all text in the first line.
3) Hit the enter key and keep typing. The second line reverts back to Arial 10pt; The div that wraps around line 2 has no style tag.