[edited from support email]
I have a Medialab experiment that triggers both questionnaires in MediaLab and IAT-timed response tasks in DirectRT. Sometimes, after the third of four tests in DirectRT (they are all right in a row), the computer locks up and I get a dialog box that says "executable RT already running" or something of that nature. Then, if I hit "OK" it continues, but it doesn't save the data from the test that it just administered.