This has been observed on Task Server 7.0 SP2 but should be applicable to all versions of task server at this point.
On the Task Server side (NS/SMP) when a task is scheduled to run and the schedule is met (or a quick run task is used), the process to queue the task on the agent and execute is passed from the Task Server to the Altiris Object Host Service. If this service is stopped or hung, as soon as it is able to receive the task from the Task Server it will do so. In this case it would happen after starting or re-starting the service.
At this time the queued up tasks would then all be passed to the clients and executed as soon as possible.
There is a timeout value within the "schedule" option of the task schedule in 7 when it is set. However this timeout value is client side based, and does not start counting down until the task has been delivered to the client for execution.
In essence there is no current resolution to this. An enhancement request KB has been created for this. See KB 49448