I noticed the following issue from /stats:

Internal Error: unable to unmarshal container info for / ({"name":"/","subcontainers":[{"name":"/docker"}],"spec":{"cpu":{"limit":1024,"max_limit":0,"mask":"0\n"}},"stats":[{"timestamp":"2014-07-30T21:51:42.316287699Z","cpu":{"usage":{"total":413129629653,"per_cpu_usage":[413129629653],"user":175480000000,"system":82170000000},"load":0},"memory":{"container_data":{},"hierarchical_data":{}}},
...json: cannot unmarshal string into Go value of type info.CpuSpecMask

I guess I know what goes wrong here, and will send out PR soon