I had Nortan Antispam before and it slowed down my internet programs since it runs a proxy. You can also try to clear out the cache and see if that works.
Its under Tools>Internet Options> Delete Files in IE. Depending on how big it is it may take a while.
You can also try looking through this site http://www.tweakxp.com/
It has lots of tweaks that are not just for IE, but for Windows XP as well.
I think drkangel is correct; I don't see any malware in your log that would cause that. You can also check:
1. Disk fragmentation.
2. Disk optimization ( noticibly improves bootup speed ).
3. Clear out all temp files and temp internet files.
4. Check your memory and page file sizes; you may need to increase one, or both.
When I installed Norton's 2004, it really slowed the performance of my system down noticebly.