I am having the same issue with my bitstamp account.  I have withdraws that show completed on bitstamp but never showed up at the receiving address.  They did reply to my ticket though and told me to wait 24 hours.  It still hasn't show up.   Right now I have open issues with bitinstant, btc-e, bitstamp, okpay and technocashier.  I'm missing funds from every one of those places and receiving no help for them.  I guess it could be linked to karma since I defaulted on a loan here on bitcointalk and my information was released on the forum.  I still plan on repaying steamboat but it seems par for the course to screw someone over when dealing with bitcoins.  Every ticket takes days to respond to.  When they finally respond they push blame back on the user and that's how you deal with it I guess.