Sorry about the problems you're experiencing.
Some ATI cards don't seem to support multiple textures, which makes crossfading in WWT not work.
But here we're talking about no images appearing at all in sky mode.
Some questions:
- What do you see when you choose SolarSystem mode? Can you see any planets there?
- Does WWT say it cannot reach the internet when you launch it even though Internet Explorer can happily go online? In that case, you can try typing 'itgproxy' in the Proxy Server box under Network and Cache in Settings.