Nothing but kudos for netstumbler, but the display is weird.
It originally comes up with about 12 minutes marked out on a s/n graph. After the 12 minutes, it pops up a horizontal scroll bar. If I wait a few minutes, then try to scroll, to see the current signal, I get a solid green bar (with a solid red bottom where the noise is). The legend on the bottom is also wrong - small pieces of each date-time. It's almost as if the form wasn't being refreshed.
Sony GRX550
Mobility Radeon 7500
Happens at any screen resolution.