With the the current matplotlib version 1.4.3 using python 3.4.1 from Anaconda on Windows 7 I tried using the new nbagg backend.

The test code is

import numpy as np

import matplotlib

matplotlib.use('nbagg')
from matplotlib import pyplot as plt

x = np.linspace(0, 4, 100)
f = lambda x: x**2 + np.cos(5*x)

plt.plot(x, f(x))
plt.show()

This gives me a plot with the interactive controls from the nbagg backend. Now I can use the pan tool and move the axis a little bit. This works 3-4 times, after than the pan tool stops work, similarly the zoom tool. The download button is the only one working, all other functions cease to run.