Router trouble..

I recently purchased a Linksys BEFW11S4 to share a cable internet connection with the other PCs in my home. Before installing the router, I always had a very stable connection but now, the host PC's connection is somewhat unreliable. When I use instant messaging programs on the host computer, I will randomly lose the connection for a breif moment but I can always reconnect. Also, sometimes it takes much longer than it should to send and recieve messages. This also happens in some internet gamesas well. However, I never experience a connection loss while using a browser. Either it doesn't affect the browser or the connection loss isn't noticable. The other PCs might be having this problem too but I'm not sure. I never had this problem withmy internet connection before so I am betting it is the router. They may be a setting that I have missed but I don't know what it is. Any help would be greatly appreciated. Thank you.