Did the XShellZ default shell environment recently remove access to X11 libraries? In December, I could compile X Windows C++ programs. (They couldn't bring up a window of course, but programs would compile and link.) Anyway, compiling with lines like "#include <X11/Xlib.h>" will now give a compiler error about not being able to find the header. Similarly, when running a X11 program I previously compiled and ran in this environment, the program now stops immediately with an "error while loading shared libraries: libX11.so.6: No such file or directory".