This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
Perhaps the <svn> task is getting confused with having both the <checkout> and <list> subtags defined. You shoudl try passing only the <list> subtag with the necessary information (such as the "url" property and "recurse"). Example: