Are you using yourdomain.com (rather than server.dreamhost.com) to connect?
Does your ftp client have the ability to list 'owner' next to your files?
My first impression would be you're currently being migrated to new hardware, second guess would be a routing (or other) problem at server level. In either case, contacting Support was your best option so you've already done the right thing
Maximum Cash Discount on any plan with MAXCASH