My last three batches of beer have had a sour taste. The first batch that suffered from this was brewed about 8 months before the second two batches, as we moved house and I hadn't got round to starting again. Could some nasty "bug" conceivably have survived in my fermentation equipment for 8 months without nourishment? I was really thorough in sterilising (VWP) before this last batch, but have just tasted a) a beer bottled 2 weeks ago, and b) a mouthful of what's currently in the fermenter, I fear I still have a problem.