I'm trying to use a VF page for some users and not for others.  In fact, I've got 2 pages I'm doing this for: an edit page and a view page.  I'm using a fairly simple action call to make this happen, but it only works on one of the pages.

<apex:page action="{!if($Profile.Name = 'Sales',null,urlFor($Action.Case.View, $ObjectType.Case, null, true))}"

 I've overridden the New and the Edit buttons with my edit page, and I've overriden the View button with my view page.

If the user is in the Sales profile everything works great.  If they are not in the Sales profile and they click the New button, it redirects to the standard New page -except the "Cancel" button won't work (it just comes back to the same Edit page) and the URL is a disaster (cs3.salesforce.com/500/e?retURL=https%3A%2F%2Fc.cs3.visual.force.com%2Fapex%2FAgentRequestEditPage%3FretURL%3D%252F500%252Fo%26save_new%3D1%26sfdc.override%3D1&nooverride=1)

If a non-Sales user tries to click on a record to view the detail, I can see they are getting redirected, but they end up at a "URL No Longer Exists" page.  Likewise, that URL is also a disaster (cs3.salesforce.com/500/d?retURL=https%3A%2F%2Fc.cs3.visual.force.com%2Fapex%2FAgentRequestViewPage%3Fid%3D500Q0000002kXar%26sfdc.override%3D1&nooverride=1)

Can someone help me with:

A) why the View page says the URL doesn't exist and

B) Why the standard page cancel button won't work after being redirected to the new page.

Thanks.