If you still can't change your desktop background with SP v 7.0 try navigating to /System/Library/Preference Panes/DesktopScreenEffectsPref.prefPane and double-clicking on it.

This is an interesting problem; please keep us up to date.

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire