Hi Scott Clancy,
This can be done easily with an "On-Demand " workflow... below are the steps,
- Create a work flow (On-Demand) on the Task entity.
- Click Add Step and select "change status " and set your desired option.
- Activate your Work-flow.
- Select the task record which you wish to re-open and select "Run Work-flow " and select the appropriate one..
Done!!!
Below is a screenshot for your reference,
http://www.box.net/shared/2v759exv5f
Cheers, Edwin