Why weren't you able to run the test? Did you try all three of the primary test sites at least once?
Questions about your setup:
What have you tried to alleviate the problem?
What else is running on the system? FTP Fileserver? bittorrent? Web Server? Messageboards? Anything else that might use bandwidth that I didn't mention? Do you share the network with any other computers?
Do you run the server CLI only or do you use the Xwindows (gnome/KDE) graphical system?
What is your connection setup? Are you Co-lo? Cable? DSL? Router? If router, what model?
Is your Realtek NIC onboard or separate PCI? Have you tried installing
Generic Drivers for the NIC? Have you tried disabling/removing your current NIC and replacing it with another one of a different brand like 3com or Intel?
What's your system utilization look like at the time you notice the lag spikes? If you do a traceroute out from your location what does that look like? Does traceroute show the lag starting right from the first hop or out a few hops from there? Can you ping sites? What do those stats look like?
Help me, help you.