Error - There is a budget for this task

We are creating a sub-task to a parent task, this parent task was budgeted earlier, but no actuals has been charged to. Currently there is a need to create a sub-task and when creating system throws an error as "There is a budget for this task". We removed the budget for this parent and still the same error, system is not letting us delete the line item as well. Any help is greatly appreciated.