Problem occurs with Matplotlib 1.3.5 coming with Anaconda3 (Windows 10, 64bit) and 2.0.0b4 installed with pip into the same Anaconda3.

Following code flashes a window (opens and closes quickly so that nothing can be seen):

import matplotlib
matplotlib.use("Qt5Agg")
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.hist([0,1,1,2,2,3,3,3,3,4,5,6,6,6,7,7,8,8,8,8,8,9])
fig.show()

When I change last line to plt.show(), then everything works fine.