Once you've connected you Ethernet cable from your PS3 to your computer go to "Network and Sharing Center" on your computer. Then go to "Change Adapter Settings" , you should see your connection and another connection named "Local Area Connection" right click on your connection and then go to "Properties" go to the "Sharing" tab, make sure that both checkboxes are ticked and the top checkbox, once you've ticked that click the little dropdown feature and select "Local Area Connection" and then press Ok. The dropdown feature is this:
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Once you've done that, go onto your PS3. Go to the network setup or whatever. And instead of going wireless, click wired and click automatic on all of the network options and then try signing in. It should work

Sorry for the sloppy reply. Don't bridge your connections, just share your connection with the local area connection which is with your PS3.