Yeah i saw that, maybe too many connections or quarkcoind used too much cpu? Or the too many files open error, I have that on my yacpool sometimes if I forget ulimit -n 1000000.
Have you seen what p2pool reports during those times, if anything? My yacpool sometimes is not reachable for a short time (~5 min) from browsers, but p2pool keeps running fine and miners submit work if i go check, I think that happens when yacoind uses a lot of CPU.