Oh well! *Blush*
However, I have used the following tools to try and discover what is launching these pop-ups, and, near as I can tell, explorer.exe itself is launching them.
–Spybot Search & Destroy
–McAfee VirusScan
–AdAware 2007
–Filemon (SysInternals)
–Procmon (Sysinternals)
–ProcXP (VERY cool util, thanks Ryan) (Sysinternals)