Are you using PS3.ProxyServer.GUI, the original? It doesn't matter if you have the English or Chinese version, but you can't be using PS3 Proxy by 3r1c.
If you are using PS3.ProxyServer.GUI, in the first tab, check PS3, make sure you fill in the IP field with the IP address of the PC you're using, and click the button. Now go to the second tab and clear *.pkg* so the field is empty.
On your PS3, set up your network connection. Pick custom for the first prompt, then auto for everything else, except enable proxy and set it to the IP of your PC. Now try to log into the PSN.
Go back to your PC and check the second tab, and it should give you a link to the file it's checking for firmware. Copy this URL, hit the button in the third tab, and paste the link on the left side. On the right side, hit the "." button and browse for the update file that you have on your computer.