
   _The_ problem with Oort cloud sources is that absolutely
   no plausible mechanism has been proposed. It would have
   to involve new physics as far as I can tell. Closest to
   "conventional" Oort sources is a model of B-field pinching
   by comets, it's got too many holes in it to count, but at
   least it was a good try...

So you have a plausible model for GRB's at astronomical distances?
Recent observations have just about ruled out the merging neutron star
hypothesis, which had a lot of problems, anyhow.  We have to look for
implausible models and what is fundamentally allowed independent of
models.

A paper on the possibility of GRB's in the Oort cloud just came
through the astrophysics abstract service.  To get a copy of this
paper, send a message to astro-ph@babbage.sissa.it with the subject
line 
  get 9304001


Here is the abstract of that paper.

   The currently favored explanation for the origin of \GRBs puts them
   at cosmological distances;
   but as long as there is no distance
   indicator to these events all possible sources which are
   isotropically distributed should remain under consideration. This is
   why the Oort cloud of comets is kept on the list,
   although there is no known mechanism for generating \GRBs
   from cometary nuclei. Unlikely as it may seem, the possibility that \GRBs
   originate in the solar cometary cloud
   cannot be excluded until it is disproved.

   We use the available data on the distribution of \GRBs (the BATSE
   catalogue up to March, 1992), and
   the Catalogue of Cometary Orbits  by Marsden and Williams (1992) to
   investigate whether there is any observational indication for correlations
   between the angular distributions of \GRBs and comets' aphelia,
   assuming that the distribution of aphelia direction reflect,
   at least to some extent, true variations
   in the column density of the Oort cloud. We also apply the $\vov$
   test to both distributions.