Outlook Web Application Stops Working

My Outlook Web Application stops working. I have to get into OWA every 45 minutes but it does not respond. So I went to the Exchange Server and refresh the webpage two times every 45 minutes just to be able to continue working and to make OWA works. It cannot access the internet then after I refreshed it the second time, it brings me back to the very beginning where I have to access OWA and send emails again. Then I need to do the whole thing again in the next 45 minutes. Why do I have to do this? Is there someone here who has encountered the same problem as mine? Please help me. By the way I am using Exchange Server 2003. I don’t know why internet also disconnects itself from the server.
