Hi
I faced the same problem and got it solved by updating the dialog_imagemap.js file.
Search the code "if(!Browser_IsWinIE()){"
And replace it with this.
//if(!Browser_IsWinIE())
//{
editor.InsertElement(oImg) ;
//} ;
This will solve the problem.
This issue is resolved on my side in both 6.3 and 6.4 version
Thanks
Yuvika