In house we have some legacy openlook apps that we are replacing with Java apps. These applications are now summarily dumping core when trying to display on the 4.0.1 server. They are fine on the 3.3.6 server. If I get a chance I'll see where they are doing it and update this message
The (remote) programs are failing on XtAppInitialize with signal 11
If the remote programs are coredumping then there is a bug in the remote applications IMHO. You would have to get a backtrace of a coring app, and track down where the problem is occuring. It likely is just a bad assumption in the app of something that has changed. It is hard to say without more info though. I have nothing here to reproduce it. Xt apps are also considered legacy as you mention, and Xt is quite unsupported by the XFree86 team for the most part. If a bug can be traced directly o XFree, and enough info supplied to fix the bug, or someone submits a patch that fixes a bug, then I'll apply it and submit it to XFree86, but I don't currently consider this a bug in XFree86.