Question: Error in sum or gamma?

I am running Maple 13.0 on Ubuntu 9.04 and I'm having Maple give me some strange outputs. 

In this first block of code, I define an expression f which I try to evaluate (unsuccessfully) at a partiuclar value of t and g.   If I expand first, then I get an answer, which is not correct.

> f := sum((-1)^j*binomial(t-j-1, 4-j)*binomial(g+t-4+j, j)*(sum(factorial(g+2*t-8)*binomial(4-j, i)/(factorial(t-j-1)*factorial(t-3+j-i)*factorial(g-4+i)), i = 0 .. 4-j)), j = 0 .. 4);
> eval(f, [g = 30, t = 20]);
Error, (in GAMMA) numeric exception: division by zero
> eval(expand(f), [g = 30, t = 20]);
                      -4922028793519545475966591968960

However, if I first define g and t then ask Maple to compute f I get zero, the correct answer.

> g := 30; t := 20;
> f := sum((-1)^j*binomial(t-j-1, 4-j)*binomial(g+t-4+j, j)*(sum(factorial(g+2*t-8)*binomial(4-j, i)/(factorial(t-j-1)*factorial(t-3+j-i)*factorial(g-4+i)), i = 0 .. 4-j)), j = 0 .. 4);
                                      0

So, how can 0 be equal to -4922028793519545475966591968960?  Any help with this strange behavior would be appreciated.