Windows Auth. Timeout after 60 minutes

[Tom Smit]

We're having a problem where our application is timing out
after 60 minutes no matter what type of activity is
occuring. A user can be in the middle of a server call
and it will timeout after 60 minutes. This only occurs
with Windows authentication and not forms based.

We have the following in the web.config:

<authentication mode="Windows">
<forms loginUrl="Login.aspx" name="RiskLogin"
timeout="120" path="/">
</forms>
</authentication>

<sessionState mode="StateServer"
stateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1;user
id=sa;password=" cookieless="false" timeout="120" />


Where is this 60 minute timeout coming from? Am i missing
something?