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Can you get a connection without your router, i.e. the PS2 plugged directly to your modem/stb, no other devices PC or router connected to the modem/stb. Remember to reboot (power off and on the modem/stb and PS2 when you swap it over. Doing so will at least establish if it's the router causing issues or not.
You may want to check your router and ensure it has any necessary ports through a firewall open.