  A microlensing event may exhibit a second brightening when the source and/or
the lens is a binary star. Previous study revealed 19 such repeating event
candidates among 4120 investigated microlensing light curves of the Optical
Gravitational Lensing Experiment (OGLE). The same study gave the probability ~
0.0027 for a repeating event caused by a binary lens. We present the
simulations of binary source lensing events and calculate the probability of
observing a second brightening in the light curve. Applying to simulated light
curves the same algorithm as was used in the analysis of real OGLE data, we
find the probability ~ 0.0018 of observing a second brightening in a binary
source lensing curve. The expected and measured numbers of repeating events are
in agreement only if one postulates that all lenses and all sources are binary.
Since the fraction of binaries is believed to be <= 50%, there seems to be a
discrepancy.
