  We demonstrate that a two brane system with a bulk scalar field driving
power-law inflation on the branes has an instability in the radion. We solve
for the resulting trajectory of the brane, and find that the instability can
lead to collision. Brane quantities such as the scale factor are shown to be
regular at this collision. In addition we describe the system using a low
energy expansion. The low energy expansion accurately reproduces the known
exact solution, but also identifies an alternative solution for the bulk metric
and brane trajectory.
