Session problems

I'm having a problem with my Application.cfm and session variables.

I have a diary / jobs list page and I'm using session variables to hold most of the variables as the screen updates between different views.

Application.cfm:

<cfapplication
name="diary"
    setdomaincookies="yes"
    clientmanagement="no"
    sessionmanagement="yes"
    setclientcookies="yes"
    sessiontimeout="#CreateTimeSpan(0, 1, 0, 0)#"
>

        <cfif not isDefined('session.diary')><cfset session.diary = "daily"></cfif>
        <cfif not isDefined('session.showNotes)><cfset session.showNotes= "N"></cfif>
        <cfif IsDefined("form.diary")>   <cfset session.diary = "#form.diary#">     </cfif>
        <cfif IsDefined("form.showNotes")>   <cfset session.showNotes= "#form.showNotes#">     </cfif>

The problem:

I have links on the pages for different options,

     Current state: Daily Diary, hide notes

Click on "pending" diary

     <input name=diary value=pending>

     Current state: pending diary, hide notes (from session.ShowNotes)

Click on "Show NOtes"

    <input name=showNotes value=Y>

     Current state: daily diary, show notes

The last state should be pending diary, show notes but the session variables seem to have been forgotten and reverted to the default.

What have I missed?