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Three bodies in an equilateral triangle with each body in a circular orbit about the center of mass is a known solution to the 3-body problem. But, in most cases, it is an unstable solution.

With this applet, you can investigate mass ratios that lead to stable Lagrange systems vs. unstable ones. If the heaviest mass is at least 24.96 times more massive than the second heaviest mass and the lightest mass is zero, then the system is known to be stable.
For the derivation of this result, see:
Linear Stability of Lagrange Points: Complex Variable Notation Technical report, Department of Operations Research and Financial Engineering, Princeton University, 2006.

The default mass values appear to produce a stable system. But, if you increase m₁ just a little bit the system becomes unstable. Even unstable solutions appear to be stable for some time. If you set "warp" to 100, the integrator will show the instability very quickly. Give it a whirl.

Note: the warp parameter only controls how often the screen is updated---large values mean that many time steps of the integrator are performed between each screen update. This makes the simulation run much faster as updating the screen image is more time consuming that a step of the integrator.