Search for the line <platform name="win32" default="Auto"> and
change it to <platform name="win32" default="net-3.5">
Search for child element <readregistry property="sdkInstallRoot"
key="SOFTWARE\Microsoft\Microsoft SDKs\Windows\v6.0A\(something)
\InstallationFolder" ... > within the <framework name="net-3.5" ... >
tag and chage the value of key to SOFTWARE\Microsoft\Microsoft SDKs\Windows\v6.0A\InstallationFolder"