Question: Error: "too many levels of recursion" when changing the limits of integration

First, here is my code (the last 3 lines are actually a single expression, despite being split over multiple lines below):

with(Statistics):
with(Student):
with(Student[NumericalAnalysis]):
Student[Calculus1][Roots]:
k := 8;
size:=5000;
h:=3.1;
Llimit := evalf((size-1)-10*sqrt(2*(size-1)));
Uplimit := evalf((size-1)+10*sqrt(2*(size-1)));
evalf(Int((Int(CDF(Normal(0, 1), h/sqrt((size-1)*(1/x+1/y)))*PDF(RandomVariable
(ChiSquare(size-1)), x), x = Llimit .. Uplimit))^(k-1)*PDF(RandomVariable(
ChiSquare(size-1)), y), y = Llimit .. Uplimit));

The integral evaluates correctly when size is 5000 (five thousand), but when I change size to 50000 (fifty thousand), I get the "too many levels of recursion" error.  Any ideas?

Thanks in advance...