http://digitalvillage.org.uk/margrove2/

upgraded to 3.2 and suddenly the background green tree images is appearing in places it shouldn't.

sorry - this is probably really obvious and I simply can't see it or it may not be an upgrade issue at all and I just did something dumb

The background of the center column is not defined and lets the body background shine through. To set a background color for the center see A. Theme Options -> Center -> Center column style