  We present L' band (3.8 $\mu m$) MMT/Clio high-contrast imaging data for the
nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to
have one -- possibly two-- faint comoving companions (GJ 758B and ``C",
respectively). GJ 758B is detected in two distinct datasets. Additionally, we
report a \textit{possible} detection of the object identified by Thalmann et al
as ``GJ 758C" in our more sensitive dataset, though it is likely a residual
speckle. However, if it is the same object as that reported by Thalmann et al.
it cannot be a companion in a bound orbit. GJ 758B has a H-L' color redder than
nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary
models, GJ 758B has T$_{e}$ $\sim$ 560 K$^{^{+150 K}_{-90K}}$ and a mass
ranging from $\sim$ 10--20 M$_{J}$ if it is $\sim$ 1 Gyr old to $\sim$ 25--40
M$_{J}$ if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e
$\sim$ 0.73$^{^{+0.12}_{-0.21}}$, with a semimajor axis of $\sim$ 44 AU$^{^{+32
AU}_{-14 AU}}$. Though GJ 758B is sometimes discussed within the context of
exoplanet direct imaging, its mass is likely greater than the deuterium-burning
limit and its formation may resemble that of binary stars rather than that of
jovian-mass planets.
