Under IE the CPUShare webserver sometime was hanging during POST submissions. I've finally tracked down this IE specific problem and all data points to an IE specific bug that has been very easy to reliably workaround by just increasing a timeout in the CPUShare webserver (without having to disable pipelining as a whole). Firefox has never been affected by this pipelining related problem, to turn on pipelining in Firefox you need to type about:config in the URL bar and then double click on network.http.pipelining.

https://www.cpushare.com/hg/Twisted/rev/dc84d9533386