Today we had some problems after our Luminis 4.3 upgrade as we missed that some of the server.xml and tomcat-cp-conf parameters had changed. In the process of trying to fix it, we changed a few parameters like maxHttpHeaderSize and maxThreads, in some cases back to where they were. Support made a few recommendations. It turned out that what was biting us is that the upgrade reversed maxHttpHeaderSize back to what it was by default rather than what we'd had on Luminis 4.2, but we didn't notice it.
Anyway, we've got everything working again except for strangely enough, Internet Explorer refuses to load the SSL version of the page. I get the extremely helpful "Internet Explorer cannot display the webpage" error, with no apparent reason for it. I'm baffled. I even tried setting another test system to a maxHttpHeaderSize of 32768 like we now have on production -- SSL appears to still work fine. Any pointers at all? The behavior is very similar to this: http://support.microsoft.com/kb/2744241
...but nothing else about our setup has changed so I can't see how that could be the case.