I had the exact same thing happen to me after months of working on a site. All other sites were still working fine remotely, but one particular site would not allow me to select a table or view a table from with DW.
Finally, I just logged into my Cpanel and deleted that user. Recreated it with a new password, added that user to the database and updated my connection file. It all works now. Not sure what happened.
TroyD