nis 2009 and firefox 3.6

on my sons laptop he has nis 2009 and using firefox 3.5.7 with both norton add ons.I read somewhere that norton was not doing a new update for nis 2009.Is this correct?I also installed nis 2010 onto his laptop has this version will support firefox 3.6 but this slowed the laptop down so i uninstalled and reinstalled nis 2009.How much of a security risk is it without the add ons if i update to firefox 3.6?