Thanks!

Yes, UPnP is configured in my DSL box.

LW chat is rather nice, lightweight, simple, and clean. AND it shows you the IP addr so you can relate things within LW such as browsing a host whilst chatting... yes? I find it very usable...

Meanwhile, the idea that my ISP is doing some throttling could explain the cause of variable results from hour to hour and day to day... hmmm.... yeah... maybe... worth checking on that!

There is more than one thing going on here... bugs, config errors, and ISP details... more detailed analysis and reports later!