Hi Gaetano I haven't seen this error before but one possibility is that you had marked a particular plot on the active chart before running the exploration. It's a fact that an exploration runs more slowly when a plot is marked (selected), and this occurs regardless of whether the exploration calls for a P (or INDICATOR) variable or not. This suggests to me that whenever a plot is marked (as it would be for use as a P variable) an exploration will attempt to use the marked plot as a P variable even if the exploration code does not call for such use. This is pure speculation on my part but the error you experienced could relate back to an unintentionally marked plot causing a problem while running an exploration. Roy