It must be apparent to DDL that people are concerned about the fact that they've paid money for goods that they haven't received, and they must have email addresses for all the people who have pre-ordered. I would have thought it should be fairly easy for them to send out a bulk email to all the people who have ordered to let them know what is happening.
Failing that, a reply to the email that I sent them would put my mind at rest a little bit.
I actually don't think that they're dodgy. At the moment my guess is that they have pre-sold more copies than they have available to them and they're panicking about what to do.