Rework to use an iframe for most of the work, rather then sajax. Still
using a sajax call for cancelation, but the main invocation uses a plain iframe. This has the added benefit of scrolling more nicely instead of jumping back to the top with each write. Looks like xmlhttprequest or its impl in at least firefox is moderately broken, so that mulitple simultaneous requests get very confused with each other, and things break.