I have custom objects created in the Vault, and in a Power Job script I want to update the properties on it.
you can use the CustomEntityService.UpdateCustomEntityProperties Method
public void UpdateCustomEntityProperties( System.long customEntityIds, PropInstParamArray propValues )
You have to pass in the entityIds of the custom objects you wish to edit and a PropInstParamArray object for each entityId. The values are applied to to the customObject with the same index as the PropInstParamArray has. If you want to apply the same value to multiple objects you have to pass in the same PropInstParamArray for every id.
Also you should make sure that the values you want to set are valid. Otherwise you get some nonsensical error message which in no way indicates that your passed in values are invalid.