I sent 518.34 from MtGox to Dwolla on Friday (6 days ago) and got no confirmation. I sent an email to
info@mtgox.com yesterday and again today but no response. I called Dwolla and they said positively there was no such transfer initiated from MtGox to my Dwolla ID.
MtGox needs a support line. But at least they should reply to inquiries about a misplaced transfer!
I also made a withdrawal on Friday 5/27 that went missing, despite having successful withdrawals before and after that one. Perhaps a whole batch of withdrawals failed to be processed that day. I emailed Mt. Gox a few hours ago.