So far it sounds like the server configuration has been compromised instead of your account.
However in the DreamHost Web Panel have you checked the Domans -> Manage Domans to make sure the domains on your account have not be set to “Redirected” instead of “Fully Hosted” ?
If they are still “Fully Hosted” I would suggest changing them to “Parked” or otherwise to force DreamHost to update the server configuration.
Also when checking for .htaccess file files make sure your client can view hidden files and also don’t forget Apache looks for them starting at the root. In otherwords, is there an /.htaccess or /home/.htaccess or /home/.glob/.htaccess or /home/.glob/username/.htaccess ? It is not enough to just check for /home/.glob/username/domain/.htaccess
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