Hmm... might be having some sort of conflict with IP addresses. Let's try something else here- putting the PS3 into the router's DMZ (demilitarized zone). This will put the PS3 outside of any protection it may get from the router's firewall (perfectly safe, there's nothing out there to harm the PS3 by doing this).
First, go into your PS3's network settings and add a specific IP address in- this will be the address the PS3 goes by to the router. make the last numbers high enough so there won't be any interference (192.168.0.140 should work). Once you save that go back into the router settings and click the Advanced tab. Now, click on Firewall Settings on the left side.
In here you should see a spot called DMZ Host. Check the box to enable this and put the IP address you gave the PS3 into the blank. Once done save the settings and see if that helps.