Asio Time Overload

Hi I am using Cubase 5 with windows 7 32bit edition, I have 4gb Ram and a roland ua1-g soundcard (external) when I load Cubase before even starting to produce a track my Asio Time is running at a quarter full Everything is running fine with the computer and soundcard but fruther I get with a track Cubase overloads and crashes, does anyone know how I can solve this problem? thank you

Complete system specs?