  We detect 1.2mm continuum emission from dust in the gravitationally lensed
Lyman break galaxy MS 1512+36-cB58. Our detected flux is surprisingly low:
relative to local starburst galaxies, cB58 appears to produce somewhat less
far-IR emission than its UV reddening predicts. After comparing several
different estimates of the source's dust content, we conclude that the apparent
discrepancy is most likely related to uncertainty in its UV spectral slope.
Alternate scenarios to account for a far-IR "deficit" which rely on a high dust
temperature or differential magnification are less satisfactory. Our result
underscores one of the risks inherent in characterizing the cosmic star
formation history from rest-UV data alone.
