Sour or astringent (Vinegar or Red Wine)
If you're fermenting WAY too hot, it may create some flavors that can seem kind of astringent, the same can happen if you're boiling your steeping grains.
A sour taste, on the other hand almost always means that you've got a infection of some kind (and it will be bacterial or wild yeast, which your photo does not look like.)
What source are you using for your yeast? The cheapest brewers yeast I can think of off the top of my head are Nottingham or Windsor, which should both ferment out reasonably clean (if a bit sweet in the case of Windsor.)