I haven't solved this problem yet, but I have narrowed it down a lot more. I know the problem has to do with the fact that I'm using the JCIFS NTLM servlet filter to implement Windows SSO authentication and tie it in to Seam Security. There's a difference in how IE obtains and sends network ID info versus how Firefox does it (essentially it seems firefox can't really do it) and that accounts for why I have no problem in Firefox, just in IE. If I disable/remove the JCIFS servlet filter, then there's no problem. It doesn't matter if I'm actually use the filter in my code. Just having the filter in the filter chain at all, appears to screw up the Ajax4JSF page refresh mechanism apparently. I'm considering hacking the servlet filter code a bit and see if I can possibly disable it after it's done its job initially - at least, for a session.