Dealing with error: "I/O error in reading pruning table"

[DougCube]

I am getting error message "I/O error in reading pruning table" but it is still providing good solutions afterwards. Should I be concerned by this message? What is the implication here? Is it talking about data generated in previous runs being cached? And if so, is there a way to force a clear of that perhaps corrupted data so it can be regenerated? Or is this talking about data generated in the current run, and if so, does this mean there may be a bug in the program?