  We re-examine critically the arguments raised against the theory that Ultra
High Energy Cosmic Rays observed at Earth are produced in Gamma Ray Bursts.
These include the limitations to the highest energy attainable by protons
around the bursts' shocks, the spectral slope at the highest energies, the
total energy released in non--thermal particles, the occurrence of doublets and
triplets in the data reported by AGASA. We show that, to within the
uncertainties in our current knowledge of GRBs, none of these objections is
really fatal to the scenario. In particular, we show that the total energy
budget of GRBs easily accounts for the energy injection rate necessary to
account for UHECRs as observed at Earth. We also compute the expected particle
spectrum at Earth, showing that it fits the HiRes and AGASA data to within
statistical uncertainties. We consider the existence of multiplets in AGASA'
data. To this end, we present a Langevin--like treatment for the motion of a
charged particle in the IGM magnetic field, which allows us to estimate both
the average and the rms timedelay for particles of given energy; we discuss
when particles of identical energies reach the Earth in bunches, or spread over
the rms timedelay, showing that multiplets pose no problem for an explosive
model for the sources of UHECRs. We compare our model with a scenario where the
particles are accelerated at internal shocks, underlining differences and
advantages of particle acceleration at external shocks.
