Did you load the "vect" package first?
By the way, it is better in general to reproduce the whole error
message, rather than just say it returned "an" error message. Also the
version information from bug_report();
-s
> In the description of the VECTSIMP function one can find the following
> remark:
> ...EXPANDCROSSCROSS refers to replacing p~(q~r) with
> (p.r)*q-(p.q)*r...
> - thus indicating that ~ should be the vector product symbol.
> But A~B gives an error message.(???)