  We discuss our radio (Australia Telescope Compact Array and Australian Long
Baseline Array) and X-ray (XMM-Newton) monitoring observations of the unusual
ultraluminous supernova SN 1978K in NGC 1313 at ~25 years after the explosion.
SN 1978K is a rare example of a Type IIn supernova that has remained bright
enough to have long-term X-ray and radio observations. The observations probe
the dense medium that was ejected by the progenitor star prior to its
explosion; the star might have been a Luminous Blue Variable. The radio imaging
shows that the source remains compact, but it may be marginally resolved. The
radio monitoring shows deviations from a smooth decay suggesting that
inhomogeneities are present in the radio emitting region. It appears that a
major change occurred in the mass-loss rate of the progenitor star shortly
before the supernova event. The X-ray emission between 2000 and 2006 is
consistent with the radiation coming from two shocks. All the X-ray data can be
fit using the same model (with no systematic evolution or short-term
variability) but this has a surprising requirement: the X-ray emitting regions
have a very large abundance of helium. This would be consistent with the X-ray
emitting shocks being located in a helium-rich layer that was ejected by the
progenitor star, or helium-rich material was ejected in the supernova
explosion. The unusual properties of the supernova motivated a search for an
associated gamma-ray burst (GRB). We show that SN 1978K was inside the ~4 sigma
error box of GRB 771029. If this association is correct, the GRB was
exceptionally underluminous. However, the quality of the gamma-ray burst
locations at that time was poor, and this is likely just a chance alignment.
