Is your connection Wi-Fi?
Sounds like some bandwith s being chewed up somewhere.
Any background programs running MSN etc torrents? I would suggest you use a virus program for a scan and also a spyware scanner. You may have some spywear on your system.
My understanding about the random ness is that Windows assigns priorities to different running programs and allocates resources acordingly.
Try this running a traceroute to blizzard. This post explains how to read it. There maybe a problem here.
http://forums.worldofwarcraft.com/th...33419319&sid=1
How to do it.
Running a Traceroute on Windows XP:
1) Go to Start (start button on the lower left of the desktop)
2) Choose 'Run'
3) Type: "cmd" (no quotes)
4) This should bring up a DOS prompt. Once there, type: "tracert domain.com" (without quotes) ... use 12.129.232.117 (blizzard logon server)
This should result in a series of hops from your computer to the server you are tracing to.
If you are running a wi/fi conection make sure its password protected.