locking up&not loading pages on internet

I have a problem if I leave my computer on for an hour or so then try to hook to the internet after it signs on all iget is page cannot be displayed. I restart the computer and the same page will load with ease. If I sign off the internet then get back on I have to restart the computer again or I will get the same page cannot be displayed. It also locks up in the middle of doing things on the internet. I have 128 mb of ram,ie 5.50, win 98se 450 mh amd proccesser.