Again, thanks to everyone for the tips. I think the problem with my previous batch was that I hadn't mixed everything together -- the later batches had a different consistency because, well, the batter had a different consistency. I made two batches this weekend, neither of which had my previous problem. I made sure that everything was well incorporated and I was prepared to start piping as soon as I was done folding so that no separation would take place. Of course, I ran into other problems. My first batch was way overbeaten -- flat, runny Macarons. In an attempt to correct my first problem, I created a much larger one. So the next morning I made a second batch -- these were underbeaten, but at least servable. Now to find the happy medium . . .