Right click your AH clipboard and pick the option that has to do with Net Status (haven't seen it in so long I don't remember what the real title is). Two line graphs should swing out on the tab. If the Variance in Delay graph is wigging out, it's generally local. Something's taking CPU time away; spyware, adware, viruses, Vista, auto-updaters, ect. None of that stuff is actually needed. If the other graph is losing it, it's a network issue.
Maybe someone here can help you go through the startup list in msconfig to get rid of background processes and updaters.