The version of riched20.dll included with Office 2007 (and optionally copied for use with UR during installation) has a bug when pasting images in some situations, and could conceivably also have other issues (for instance, when selected images in tables).
Try closing UR and deleting riched20.dll from its installation path. If that resolves the freeze problem, but since you may be depending on improved table presentation features of newer version of the rich edit control, you could try a newer version than the system one (but older than the Office 2007 one); one of them is available at
ftp://ftp.kinook.com/RICHED20.zip
http://www.kinook.com/Forum/showthre...?threadid=1026
Beyond that, you may need to avoid selecting images within tables.