A new virus, a worm to be more exact has been discovered to be transmitted by Skype and to affect the same program. It's called W32/Skipi.A (as dubbed by F-Secure) or W32Pykspa.D. (the name Symantec gave it) and you can get it by clicking on a link in a conversation.
This is not something new, the same type of virus has been plaguing Yahoo! Messenger for quite some time now. Once you get the virus, you start sending messages to the ones in your list, the type that seem to be realistic and in those messages the virus will include a link to what seems to be a picture. When you click it, you get prompted by Windows to download a file. Of course, if you do download it, you will get the virus on your machine. As seen on Skype's blog, the worm uses Skype's public Application Program Interface (API) to access the PC.
And here's how to avoid viruses such as this one - when you get such a message with a link in it and it seems dubious, ask the person that sent it to you what's with the link. And if he asks you back what link you're talking about, it's quite clear that's a virus. Also, my native language protects me from such viruses - the chat message you will receive will be in either Latvian, English or Russian so when I see a chat message that's not in my mother tongue, things already start looking weird. So, before clicking on such a link ask yourself why would your friend chat with you in a foreign language.
But if you do get the virus and your AV does not protect you, you can root it out, in good old safe mode. You do need to be a little computer-savvy to do this, though. Here's a link to the solution.