Cookie Encryption and Decryption giving errors

Hi all,

This following problem has really started to frustrate me.  Being new to the platform ive largely been using quickstart and tutorial code to create a login system for a website im developing.  The problem is that cookie encryption seems to be not working at all.  I have been unable to locate any previous examples of my error.  Please Help

// Login code
// This just places some user details into a pipe separated list e.g.
// 1|DFGEG34534sgdfgdfg34|Admin|Member|Visitor
string strUserData = objMember.MemberCookie();

FormsAuthenticationTicket objTicket = new FormsAuthenticationTicket(1,
      objMember.strFirstname,
      System.DateTime.Now,
      System.DateTime.Now.AddHours(12),
      true,
      strUserData,
      FormsAuthentication.FormsCookiePath);

// THIS FUNCTION IS RETURNING NULL EVERY TIME.  Im not sure why
string strHash = FormsAuthentication.Encrypt(objTicket);                  
if ( null == strHash)
{
      throw new ApplicationException("An error occurred while hashing the user data.");
}

HttpCookie objCookie = new HttpCookie(FormsAuthentication.FormsCookieName, strHash);

objCookie.Expires = System.DateTime.Now.AddMonths(2);
System.Web.HttpContext context = System.Web.HttpContext.Current;
context.Response.Cookies.Add(objCookie);

FormsAuthentication.RedirectFromLoginPage( objMember.strFirstname, true );


// Authenticate_Request Code
string strCookieName = FormsAuthentication.FormsCookieName;
HttpCookie objCookie = Context.Request.Cookies[strCookieName];

if(null == objCookie)
{
      // There is no authentication cookie.
      return;
}

FormsAuthenticationTicket objTicket = null;
try
{      
      // BREAKING IN HERE AGAIN
      objTicket = FormsAuthentication.Decrypt(objCookie.Value);
}
catch(Exception ex)
{
throw new ApplicationException("An error occurred while hashing the user data." + (ex).ToString());
}

if (null == objTicket)
{
      // Cookie failed to decrypt.
      return;
}

// gets the pipe separated cookie data
Components.MemberDetails objMember = new Components.MemberDetails();
objMember.RetrieveCookieData(objTicket.UserData);

// Parse the role names
string[] arrRoles = (objMember.strMemberRoles).Split(new char[]{'|'});

// Create an Identity object
FormsIdentity objID = new FormsIdentity( objTicket );

// This principal will flow throughout the request.
GenericPrincipal objPrincipal = new GenericPrincipal(objID, arrRoles);
// Attach the new principal object to the current HttpContext object
Context.User = objPrincipal;

Any help would be much appreciated
Cheers
Matt