What is the source, an RTMP encoder or MediaCaster stream? I think this error in nDVR indicates either A/V sync problem, or timecodes problem in the source stream. You can configure the tolerance for A/V sync with the dvrAllowableAVPacketDelta Property, the usage is explained in the
advanced dvr article. Also look at the dvrPacketSortTime Property in that article.
If it is timecode problems, you should see log messages for the live source.