It could well be the reason- your ISP would have DNS servers and even if the mac doesn't use them the PS3 does. You may also want to put the PS3 into the DMZ, meaning it is out in the open on the internet. There is nothing in the way of virii, trojans, etc. to affect it and will be safe.
That error message is telling you there is a communication problem between the router and the PS3. Hopefully once you get the DNS numbers from your provider and put those in things will work out.