I just tested this on my machine and it works fine from several different computers and browsers. I am running Server 2008 64-bit with IIS 7.0. Are you using QVWS or IIS? It's possible this issue just occurs with the native QVWS (in which case it's just a bug that needs to be reported)...
Not sure if this exactly related but there was a bug fix related to Lost Connection issues with AJAX. A new update to SR3 has been released.
See post below: