  We are carrying out a sensitive blind survey for neutral hydrogen (HI) in the
Virgo cluster and report here on the first 5\deg\ x 1\deg\ area covered, which
includes two optically-dark gas features: the five-cloud ALFALFA Virgo 7
complex (Kent et al. 2007, 2009) and the stripped tail of NGC 4522 (Kenney et
al. 2004). We discover a sixth cloud and low velocity gas that extends the
velocity range of the complex to over 450 km/s, find that around half of the
total HI flux comes from extended emission rather than compact clouds, and see
around 150 percent more gas, raising the total HI mass from 5.1 x 10$^8$
M$_\odot$ to 1.3 x 10$^9$ M$_\odot$. This makes the identification of NGC 4445
and NGC 4424 by Kent et al. (2009) as possible progenitors of the complex less
likely, as it would require an unusually high fraction of the gas removed to
have been preserved in the complex. We also identify a new component to the gas
tail of NGC 4522 extending to ~200 km/s below the velocity range of the gas in
the galaxy, pointing towards the eastern end of the complex. We consider the
possibility that NGC 4522 may be the parent galaxy of the complex, but the
large velocity separation (~1800 km/s) leads us to rule this out. We conclude
that, in the absence of any better candidate, NGC 4445 remains the most likely
parent galaxy, although this requires it to have been particularly gas-rich
prior to the event that removed its gas into the complex.
