My Internet hasn't been working since this morning. It's a wireless connection shared with a host computer, which I am typing this on. It appears to only be my computer which is affected, and this is despite the fact that the wireless connection is running on the bottom right corner of my screen, as it always does.

When I click on Firefox all I get is a 'problem loading message'. Is this a virus or something? Or do I just need to press a few buttons....?