Random number generators always follow the same pattern, which means that when the last generated value is known you can always predict the next one, it's a machine after all.
Let's say you have such a function
int random_base(int seed);
which outputs a value between 0 and 65000, then your default random(var range) will be calculated somewhat as follows if I'm not mistaken:
var random(var range)
{
var value;
seed = random_base(seed);
value = seed/65000.0*range;
return value;
}
where seed is some global integer. You can change the seed number by calling random_seed(int num), and when you call the latter with num = 0, I assume the computer will take some additional information like the system's time (at game start) or something like that.
If you call random_seed() over and over you mess with the random(_base) pattern and in the worst case just get the same number over and over.