Hi Tracey,
Are you in a task view -- Gantt chart, Task Usage etc? The task drivers
button will not function in a resource view.
Are you using the beta version with Tech Refresh? I had a similiar problem
months ago and was able to correct the problem by exiting Project, deleting
the Global.MPT file and letting Project re-create it when I restarted
Project..
I hope this helps. Let us know how you get along.
Julie