The only place that error occurs is in CBC/HB v5. It means there is a file with the same name as your study with the extension .restart, e.g. "mystudy.restart". Normally this data is used to continue a canceled run, or to do more iterations if the study has not converged.
It may have been created by ACBC/HB or CBC/HB v4, but it does not contain the correct information for restarting a run in CBC/HB v5.
You should be able to delete the file and estimation will proceed just fine.