First of all thanks for this contribution, it works great.
Unfortunately you used an old version of htmlarea that doesn't support opensource and standards aware browsers like mozilla, netscape and opera.
I had some experience with the latest htmlarea and it worked perfecly on IE and Mozilla.
Do you think you could upgrade it ?
As for the image editor, here is a link to the one I'm using on another site, I think it is even better than the one included (and it works with htmlarea 3.0), it features a complete image editor (resize, flip, rotate):
image manager + image editor for htmlarea (by wei): http://www.zhuo.org/htmlarea/?nid=68
htmlarea 3.0: http://www.interactivetools.com/iforum/P15734/
Unfortunately wei's demo is not working at the moment because of a right error on the php files, but if you want to see how it looks like I will set you up a test page in some time.
Hope this helps and thanks again for this great contrib !