There is a nice web app, to look for your lost btc withdrawals from Gox giving possible reasons( Mine is showing LT : Large Transaction Size)
http://skanner.net/MtGox/mtgox_tx.phpSupport tickets takes 4-5 days to be responded, as they have huge backlog.
Lots of delayed transactions which are showed "LT" there, actually have spent outputs if you try to push them on blockchain.info