Form authentication persistant cookie/ticket not working

My original code for creating a persistant Forms authentication cookie/ticket used to work perfectly before. However, (I believe) as a result of the recent upgrade to .NET Framework 3.5, it has stopped working and I have lots of people at work mad at me since their cookie expires after 10 minutes of inactivity.

The authentication setting in Web.Config file is pretty straight forward: <authentication mode="Forms" />

And my code for creating a user ticket uses the function CreateUserTicket and the redirection is handled by the function RequestLogin.

Even though both the cookies in the CreateUserTicket functions are set to expire after 30 days, the user is redirected to the login page after 10 minutes.

And the Page_Load code for Login.aspx is also attached. It basically checks to see if the user is authenticated.

Finally, I have a "Base Class" for all the aspx pages and the OnLoad Event checks to see if the the "UserInformation" cookie is valid or not:
public class BasePage : System.Web.UI.Page
{
    protected override void OnLoad(EventArgs e)
    {
        if (User.Identity.IsAuthenticated && Request.Cookies["UserInformation"] == null)
        {
            FormsAuthentication.SignOut();
            Response.Redirect("~/Login.aspx");
        }
        base.OnLoad(e);
    }
}

So my question is, what am I missing in my code. I have spent quite a deal of time researching this, but I haven't been able to fix this problem yet.

Please, any help would be appreciated. I am using .NET Framework 3.5

void CreateUserTicket(short userId, bool rememberMe, string userName, string application)
    {
        FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(
            1,
            Convert.ToString(userId),
            DateTime.Now,
            DateTime.Now.AddDays(30),
            rememberMe,
            UserProfileBLL.GetUserRoles(userName, application),
            FormsAuthentication.FormsCookiePath);
 
        // Encrypt the cookie using the machine key for secure transport
        string hash = FormsAuthentication.Encrypt(ticket);
        HttpCookie authCookie = new HttpCookie(
            FormsAuthentication.FormsCookieName, // Name of auth cookie
            hash); // Hashed ticket
 
        // Set the cookie's expiration time to the tickets expiration time
        if (ticket.IsPersistent)
        {
            authCookie.Expires = ticket.Expiration;
        }
        // Add the cookie to the list for outgoing response
        Response.Cookies.Add(authCookie);
 
        UserProfile userProfile = UserProfileBLL.GetUserProfile(userId);
        HttpCookie userInfoCookie = new HttpCookie("UserInformation");
        userInfoCookie.Values.Add("FirstName", userProfile.FirstName);
        userInfoCookie.Values.Add("LastName", userProfile.LastName);
        userInfoCookie.Values.Add("Email", userProfile.Email);
        userInfoCookie.Values.Add("App", application);
        userInfoCookie.Expires = DateTime.Now.AddDays(30);
        Response.Cookies.Add(userInfoCookie);
    }
 
    void RequestLogin()
    {
        // Redirect to requested URL, or homepage if no previous pagerequested
        string returnUrl = this.Request.QueryString["ReturnUrl"];
        if (returnUrl == null) returnUrl = ResolveUrl("~/Default.aspx");
 
        // Don't call FormsAuthentication.RedirectFromLoginPage since it
        // could replace the authentication ticket (cookie) we just added
        Response.Redirect(returnUrl);
    }
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (User.Identity.IsAuthenticated)
        {
            RequestLogin();
        }
        else
        {
            ((Literal)Master.FindControl("liLoginStatus")).Visible = false;
            ((ComponentArt.Web.UI.Menu)Master.FindControl("Menu1")).Visible = false;
        }
    }

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