Connection to certain programs dropping while O/L

Can someone tell me why this is happening? If I leave my computer on for a long time, maybe 2-3 hours while online, even if I don’t get disconnected from the internet, certain programs such as Yahoo Messenger, Trillian and my Callwave service disconnect at the same time. Is there some sort of setting that will correct this, or why is this happening? My internet connection is definitely still live. Thanks!