  The existence of flux-ratio anomalies between fold and cusp images in
galaxy-scale strong-lens systems has led to an interpretation based on the
presence of a high mass-fraction of cold-dark-matter (CDM) substructures around
galaxies, as predicted by numerical N-body simulations. The flux-ratio anomaly
is particularly evident in the radio-loud quadruple gravitational lens system
CLASS B2045+265. In this paper, new high-resolution radio, optical, and
infrared imaging of B2045+265 is presented which sheds more light on this
anomaly and its possible causes. First, deep Very Long Baseline Array
observations show very compact images, possibly with a hint of a jet, but with
no evidence for differential scattering or scatter broadening. Second, optical
and infrared observations with the Hubble Space Telescope and through
Adaptive-Optics imaging with the W. M. Keck Telescope, show a previously
undiscovered object -- interpreted as a (tidally disrupted) dwarf satellite
based on its colours and slight extension -- between the main lens galaxy and
the three anomalous flux-ratio images. Third, colour variations in the
early-type lens galaxy indicate recent star-formation, possibly the result of
secondary infall of gas-rich satellites. A population of such galaxies around
the lens system could explain the previously discovered strong [O II] emission.
However, spiral structure and/or normal star formation in the lens galaxy
cannot be excluded. In light of these new data, we propose a lens model for the
system, including the observed dwarf satellite, which reproduces all positional
and flux-ratio constraints, without the need for additional CDM substructure.
[abridged]
