Norton does seem to have problems with the amount of resources used. You could try taking off Norton and putting AVG free antivirus on...click here. If your problem does not return then Norton is to blame.
It is unusual for Norton t6o cause so many problems so you may like to consider increasing your ram or closing some running applications. Start-run and type msconfig...go to the start up tab and uncheck everything that is not needed. click here will tell you what is and what is not needed at start up or post any queries in a separate thread.