So I set up my fixie with all brand new stuff, new wheels, new cog, new cranks/BB/chainring, new chain.
When I first test-rode it (like in the first couple hundred feet) it felt like the chain jumped a tooth or something, 2 or 3 times.
Last night I went for my first significant ride (4 miles maybe?) and it did it once more. It only happens when I'm really mashing on the pedals.
Is it something to do with the chain "breaking in"? I noticed after my ride that my chain, which was tight to the point of no slack (but not too tight, I followed Sheldon Brown's chain tightening instructions more or less) now has some slack in it (although not so much that I could really see the chain skipping, it's still pretty good... I've seen plenty of single speeds with more chain slack).