I'm no expert so perhaps, but I can't see how the isp could tell if the ip is static or has been dynamically assigned. unless his isp doesn't allow a LAN config at all (or more specifically more than one ip behind the isps ip). perhaps he should try connecting the ps3 without the pc connected, ditch the static ip and port forwarding and connect the ps3 to the router same as the pc does. Try it with the pc off tho. You should at the very least be able to get the browser going.
that said, i'm sure your isp would have gone through basic network settings on both the router and ps3 and what you've tol us sounds fine. Can you clear up what you meant by it happening even when the ps3 is just plugged in?
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