I went to the Microsoft tech roadshow the other week and managed to pose this question to a guy there. He has just got back to me with the answer, and it works a treat
Put this in the web.config for the app
<httpHandlers>
<add verb="*" path="*.aspx"
type="System.Web.UI.PageHandlerFactory" />
</httpHandlers>
<httpModules>
<add name="Session"
type="System.Web.SessionState.SessionStateModule" />
<add name="FormsAuthentication"
type="System.Web.Security.FormsAuthenticationModul e" />
<add name="UrlAuthorization"
type="System.Web.Security.UrlAuthorizationModule" />
</httpModules>
They need to be reinstated for .Net apps as sharepoint does something that overrides these settings.
Also look at
http://support.microsoft.com/default...b;en-us;828810
Thanks for all you help.
Chris