etch ships with CONFIG_IP_ROUTE_MULTIPATH_CACHED (experimental) enabled in the kernel. This breaks the multipath route behavior in iproute. As the google search shows, it is wreaking havoc with anyone using multipath and dual-wan systems. Those who upgraded this morning to the new stable may be in for a ride. This is a known and documented issue but cannot be found in debian's bug tracking system. This issue is not unique to Debian but it should not have passed through the release engineering for the new stable release.