Its has been a bit of struggle trying to work this out. I was trying to stop LibreOffice (version 3.4.3) showing borders around graphics. At first I thought these were real borders (either around the graphic or the frame), but then realised that they are just "view" borders and do not print. Even so, I wanted to get rid of them, but there is not option in the "view" menu.
On the Mac I discovered that in Preferences->LibreOffice->Appearance there is a check on "Object Boundaries", un-checking this does the trick. In Windows this is in Tools->Options->LibreOffice->Appearance