Highly excited electronic states of molecular clusters with intermediate-shell vacancies are calculated and analyzed using large scale ab initio Green's function calculations. In sharp contrast to molecules, an intermolecular Coulombic mechanism has been found to lead to an ultrafast decay of singly and doubly ionized states with vacancies in the inner-valence region. Small hydrogen-bonded (HF)(n) clusters (n = 2-4) have been selected as explicit examples to illustrate the proposed decay process, which does not occur in the HF monomer. The decay mechanism and the main factors that exercise an influence on it are discussed. The corresponding decay widths are estimated in selected cases, showing that the lifetimes of the states are of the order of few femtoseconds.