  We present MAMBO 1.2 mm observations of five BzK-pre-selected vigorous
starburst galaxies at z~2. Two of these were detected at more than 99.5%
confidence levels, with 1.2 mm fluxes around 1.5 mJy. These millimeter fluxes
imply vigorous activity with star-formation rates (SFRs) approx. 500-1500
Msun/yr, confirmed also by detections at 24 microns with the MIPS camera on
board of the Spitzer satellite. The two detected galaxies are the ones in the
sample with the highest SFRs estimated from the rest-frame UV, and their
far-IR- and UV-derived SFRs agree reasonably well. This is different from local
ULIRGs and high-z submm/mm selected galaxies for which the UV is reported to
underestimate SFRs by factors of 10-100, but similar to the average BzK-ULIRG
galaxy at z~2. The two galaxies detected at 1.2 mm are brighter in K than the
typical NIR-counterparts of MAMBO and SCUBA sources, implying also a
significantly different K-band to submm/mm flux ratio. This suggests a scenario
in which z~2 galaxies, after their rapid (sub)mm brightest phase opaque to
optical/UV light, evolve into a longer lasting phase of K-band bright and
massive objects. Targeting the most UV active BzKs could yield substantial
detection rates at submm/mm wavelengths.
