  An extensive dataset for SN 2003hv that covers the flux evolution from
maximum light to day +786 is presented. The data are combined with published
nebular-phase infrared spectra, and the observations are compared to model
light curves and synthetic nebular spectra. SN 2003hv is a normal Type Ia
supernova (SN Ia) with photometric and spectroscopic properties consistent with
its rarely observed B-band decline-rate parameter, Delta m_15 = 1.61 +- 0.02.
The blueshift of the most isolated [Fe II] lines in the nebular-phase optical
spectrum appears consistent with those observed in the infrared at similar
epochs. At late times there is a prevalent color evolution from the optical
toward the near-infrared bands. We present the latest-ever detection of a SN Ia
in the near-infrared in Hubble Space Telescope images. The study of the
ultraviolet/optical/infrared (UVOIR) light curve reveals that a substantial
fraction of the flux is "missing" at late times. Between 300-700 days past
maximum brightness, the UVOIR light curve declines linearly following the decay
of radioactive Co56, assuming full and instantaneous positron trapping. At 700
days we detect a possible slowdown of the decline in optical bands, mainly in
the V band. The data are incompatible with a dramatic infrared catastrophe.
However, the idea that an infrared catastrophe occurred in the densest regions
before 350 days can explain the missing flux from the UVOIR wavelengths and the
flat-topped profiles in the near-infrared. We argue that such a scenario is
possible if the ejecta are clumpy. The observations suggest that positrons are
most likely trapped in the ejecta.
