If the error message always mentions Norton, it's possible that there could be a problem with Norton itself, that malware has compromised Norton, or that too many background processes are causing system resource issues.
You've already checked for spyware - when you scanned for viruses, did you use Norton? If you haven't already, you could try an online virus scan (assuming the machine is stable enough to make it through the scan) - I often recommend HouseCall
http://housecall.trendmicro.com . . . This helps to make sure a virus hasn't got past Norton and then caused it grief.
If you've already run LiveUpdate recently, and the problems persist, you could try uninstalling/reinstalling the software & running LiveUpdate yet again.
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The system resources angle can be checked easily: right-click My Computer, choose "Properties", choose "Performance" and note the percentage of resources available. When in the 80% to 90% free range, Win98 runs well. Lower than 70%, and some programs have trouble. If you suspect a system resources issue [in this particular case, there are many other possibilities], it can't hurt for you to read up on the system resource situation in Win9x. There's a good overview over at pacs-portal -
http://www.pacs-portal.co.uk/startup_index.htm - - - The article helps explain how to use the msconfig utility to narrow down issues. Using that utility, you can limit the programs starting at system startup - if Norton's memory issues disappear, you can then consider which programs you can live without running all the time, or which might benefit from an update or patch to fix it's "memory-leak" problem.
. . . Gary