Strang error while fitting data

Hello,
I am fitting an histogram to a pol1 (linear). This is histogram is the result of the integration of a stochastic differential equation, so the values vary from one execution to another, but the histogram’s shape is always the same if I have the same input parameter. However, I often (9/10 of the times) get that error message :
Info in TMath::BetaCf: a or b too big, or itmax too small, a=0.5, b=48, x=nan, h=nan, itmax=500
Info in TMath::BetaCf: a or b too big, or itmax too small, a=0.5, b=48, x=nan, h=nan, itmax=500

What does it mean, and what may cause it ?

It is not systematic however, because the program sometimes fit the histogram correctlly.

Ok, never mind, I found what happened. There were sometime some infinite values in the histogram.