Is it just not letting you start the update at all? or is it some kind of error? Because if you are using the PS3 to make this post then the PS3 is obviously it's picking up the same WiFi signal that the Wii uses.
Try turning off the Media Server Connection in the Network settings. Also go to Settings and Connection Status List and make sure everything is okay. Make sure the connection is Enabled, check the signal strength and make sure it's on wireless.
I don't know what's wrong with your PS3 but you can atleast start with these things.