Moving this issue from bug 2723, comment #7: ==12286== Conditional jump or move depends on uninitialised value(s) ==12286== at 0x4A9256: Fl_X::make_xid(Fl_Window*, XVisualInfo*, unsigned long) (in /home/astrand/ctc/client/tlclient/tlclient.bin) ==12286== by 0x417C12: MainWindow::MainWindow(std::string, std::string, std::string) (tlclient_mainwindow.cc:388) ==12286== by 0x41076D: TLClient::runApplication() (tlclient_tlclient.cc:433) ==12286== by 0x40FA95: main (tlclient_main.cc:288) Google finds a few hits for this, such as http://starurchin.org/dillo/valgrind/18ede8e10fe2910aaab38c14ffc0842106f2aae6.html. This warning does not happen with the previous client, but I think this is because these problems are specific to the 64 bit client. See also: http://www.fltk.org/str.php?L2637 According to that STR, everything should be fine since r8732. Perhaps the problem is some of our patches? I've tried the FLTK demo programs, but cannot see the problem there.