  We present a study of the effective action approach to incorporate
higher-order effects in e^+e^- -> n fermions. In its minimal version, the
effective action approach is found to exhibit problems with unitarity and
high-energy behaviour. We identify the origin of these problems by
investigating the zero-mode solutions of the Ward Identities. A numerical
analysis of the importance of the zero-mode solutions is presented for
four-fermion production processes.
