hi John
On the first screen in the admin console after you select install application below the text box where you specify the file to be uploaded I think there is another text box that asks for the context root if its a WAR you are deploying.
Another route I have used in the past, which I'm not 100% sure of the impact it would have on deploying WARs in the same way on the same server (I'm sure someone in here will tell me) ,is to use the default EAR that comes with WebSphere. In the application.xml of the default EAR all you need to do is add your WAR and remove any other WARs that are associated with the Default EAR. Export the EAR which only has a reference to your WAR and
you should be able to deploy it without the context root error. Not the best solution but when your under pressure it may save your eardrums a bashing from the man in the suit.