Just ignore it, it's not a virus, had the same problem. I disabled the anti-spyware in the firewall, no need since i also run a virus scanned in the background. and i dont think that mirc have anything to do with your "slow-downs", and i must ask, what virus protection do you use along with the firewall? i noticed that Norton realy can mess upp things for the user that have it on hes computer. If you think your computer are infected with something, then go to this page and do a scan.
http://www.bitdefender.com/scan8/ie.html 
