you're at oxford aren't you?

this worked for me...

VanDet:=proc(n) local V;
V[n]:=VandermondeMatrix(<seq(x[i],i=1..n)>);
factor(Determinant(V[n]));
end proc:

(cheater)

hmm well anyway i managed to mess around with proccesses and stuff so it's worked out alright anyway, although it's not very elegant.

don't worry about it any more, for some reason it was having problems rounding numbers inside a vector, so i dotted itt with <1,x,x^2,x^3,x^4> to turn it into a polynomial then used evalf[3] and it worked fine.

make sure the account you are using is an administrator account, I had the same problem, I could only make it work by using an administrator account.