  Gamma-ray bursts are powerful probes of the early universe, but locating and
identifying very distant GRBs remains challenging. We report here the discovery
of the K-band afterglow of Swift GRB 060923A, imaged within the first hour
post-burst, and the faintest so far found. It was not detected in any bluer
bands to deep limits, making it a candidate very high redshift burst (z>11).
However, our later-time optical imaging and spectroscopy reveal a faint galaxy
coincident with the GRB position which, if it is the host, implies a more
moderate redshift (most likely z<2.8) and therefore that dust is the likely
cause of the very red afterglow colour. This being the case, it is one of the
few instances so far found of a GRB afterglow with high dust extinction.
