Sometimes this error can be rectified by going to Domains -> Manage Domains, clicking Edit on the relevant domain and clicking Redirect this domain now!, without actually making any changes. This causes the Apache config file to be rebuilt.
If this fails, contact DreamHost support detailing the problem. I am sure they will sort it out for you.
Save [color=#CC0000][b]$50[/b][/color] on DreamHost hosting using promo code [color=#CC0000][b]SAVEMONEY[/b][/color] ( Click for promo code details )