Fixed deadlock when cross instantiating conditional singletons

Ignore-this: b341251ee799d3930257245db7ea0fce

darcs-hash:20130129083220-b22ec-e06b7d56d87158011b991c37ab62e36846eb69e4
Removed extra cehcks on SDP origin field

Ignore-this: 2db986e5a8af5e36d9c6bd3dbcf995df

darcs-hash:20130204143107-56b4d-5f8b291578961c6bd2b288fbcc73be851a54127d