Problem with pages loading

I have an AMD Athlon 2100+ with 512 MB DDR ram running on Windows XP Professional with SP2. For awhile now, Ive been having a problem where pages sometimes wont load. Then after a little while they load again and then the problem reoccurs. Im using IE. It happens whether I am using a wired lan or wireless. What could be causing this? I have scanned for viruses and spyware and cleaned it and also reset the IE settings. Any ideas?