Hi, I may have found a bug in how the clr package converts .net exceptions to Python exceptions, at least as it relates to PyQt. If I try and add a library which does not exist, and then try and print the exception, PyQt is subsequently unable to initialize OLE. This means that PyQt applications cannot use copy/paste and drag-and-drop. Here is a minimal example: import clr import sys from PyQt4 import QtGui try: clr.AddReference('foo') #This doesn't exist except Exception as e: print e app = QtGui.QApplication(sys.argv) app.exec_() This results in the Qt error: Qt: Could not initialize OLE (error 80010106) The program runs, but copy/paste and drag-and-drop fails. If I do not try and print the exception (replace the except block with 'pass'), the program runs without any problems. Also, if the library exists I have no problems. Is this something anyone has seen before? Thanks! Jonathan Mizrahi