You can refresh the internet content by doing the following:-
1 Press 'Internet Video'
2 Scroll horizontally until you see 'Settings'
2 Scroll vertically until you see 'Network'
4 Scroll down to 'Refresh Internet Content'
With regards the wireless dongle, you can only use the one made by Sony, which I have just disconnected and replaced with a powerline bridge!
I disconnected it, because my wireless wasn't strong enough in the living room and the picture on Iplayer kept stopping.
So I have now disconnected the wireless dongle and fitted a Netgear XAVB2001 powerline bridge (£74 from Ebuyer).
http://www.netgear.com/products/home.../XAVB2001.aspx
I plugged 1 unit into the mains next to my router and the other next to the Bravia and it worked 1st time. Simple bit of kit that essentially turns any power socket into a LAN port.
I have just watched some iplayer material on the higher definition option without any break ups - this was impossible with the wireless set up I used before.
Also, if you do use the wireless dongle, it's another (slight) delay when starting up your TV, while the Bravia 'detects' all the devices!
If you do want a dongle, my redundant one is only 4 weeks old?