Doesn't sound like a bacteria infection at all. Sounds like common esters. I have had this before, and would describe it as a sour bite. My girlfriend thought it was vinegary as well.
This is pretty common when fermentation temperatures either fluccuate or are a bit too warm for your yeast. It wouldn't be out of the ordinary to get some ester if your temp was at 68. Remember, even if the room temp is 68, the fermentation temp is going to be 2-5 degrees higher than that inside the primary. The room/chamber temp should be about 60-62 to hit an optimal ferm temp around 65-68 for most common ale yeast. If it is esters, I bet you had a relatively fast fermentation that produced lots of activity for about 2-4 days, then almost no activity after that. I would also bet that you are about 2-4 weeks out from your brew day.
Anyway, the good news is that esters mellow out. Let the beer condition for about another 3-4 weeks at room temp or 4-6 weeks if you've already chilled it, and the ester taste will be gone.