Don,
Nowadays browsers have multiple processes, TC can't handle that.
The only way you can do what you want is by running a bat in the beggining of each test that kills all the processes and launches the browser again.
set up a bat with this code (change the name of the browser to the browser you work with):
taskkill /f /im "iexplore.exe"
start iexplore.exe
Add this bat to your TestedApps on TC, on Events->GeneralEvents go to the "Test Engine Events" and on the "OnStartTest" event add the code to run that TestedApp you just added.
I can't put it much better than this.
