Virus Causing Frequent Internet Disconnection/Freeze?

Hey guys, I'm new to this forum and require quite a bit of help.

 

Lately, I've been disconnected from msn continuously and I've been wondering if there was a virus that would do such a thing? (I am very bad with computers.) Also, whenever i download anything, the download freezes (I think the internet disconnects) usually after downloading 5 MBs. I am currently using Mozilla Firefox. Whenever my internet disconnects, my modem would usually lose its ethernet light, but it doesn't happen with this "thing" that is happening to me right now. 

 

I have tried a full system scan and NAV managed to remove a W32. IRC bot and that was it.

 

Please help me.