Shadows around imported PNG

[hdebeer]

Hallo I have experience this before, but I would like to know what it causes.I have imported PNG into Xara Wed Designer but upon preview it shows a shadow / rectangle behind the picture which I did not put there
Also with the logo on top left I have just added the pictures it does the same. I have added a background picture and it seems to do that everytime I added a background
It only does It do png imports pictures but with other designs that I do on Xara which has a transparent background.
Thank you