Weird internet problem

well I am connected to the internet throuugh a modem wich sends wireless signal. I am able to connect to use Internet explorer, dowload crap and stuff, but when I try use a program like Limewire, Ares, Utorrent or internet games like Ragnarock Online or Maple Story it can't connect to the server/network and my sister, who is recieving signal from my modem can use Limewire.
does anyone knows what is the problem and/or a solution