Download and install spybot S&D, immunize your computer, then scan for spyware and remove anything that is found.
You should also get some antivirus software to scan your computer. I would recommend ESET NOD32 Antivirus (Version 5). The trial version is free for 30 days. Conduct a full computer scan and post your results on whether anything was found.
Kaspersky and Bitdefender rate very high if you need alternatives, but I have no experience with either so I cannot recommend them.
-Blue
Another possibility you could try is a fresh re-install of the game (No mods, saves, etc etc. W/e User-added content) and see if it still does it.
I doubt that would work. It thinks the launcher is a virus, not the client.