What if you modify the code like this, also making it more maintainable:
Application.cfc
<cfcomponent
output="false"
hint="I define the application settings and event handlers.">
<!--- Define the application settings. --->
<cfset this.name = hash(getCurrentTemplatePath()) />
<cfset this.applicationTimeout = createTimeSpan( 1, 0, 0, 0 ) />
<cfset this.sessionTimeout = createTimeSpan( 0, 0, 20, 0 ) />
<!--- Set up the application. --->
<cfset THIS.SessionManagement = true />
<cfset THIS.ClientManagement = true />
<cfset THIS.SetClientCookies = true />
<cfset THIS.loginStorage = "Session" />
<cfset THIS.clientStorage = "sidys" />
<!--- Define the request settings. --->
<cfsetting showdebugoutput="false" />
<cffunction
name="OnRequestStart"
access="public"
returntype="boolean"
output="true"
hint="Fires at first part of page processing.">
<!--- Define arguments. --->
<cfargument
name="TargetPage"
type="string"
required="true"
/>
<cfset SetLocale("fr_FR") />
<cfif IsDefined("Form.logout") or IsDefined("URL.logout")>
<cflogout />
</cfif>
<cflogin idletimeout="1200">
<cfinclude template="form.inc" />
<cfif isDefined("cflogin.name") AND cflogin.name IS NOT "" AND cflogin.password IS NOT "">
<!--- login form submitted, with username and password filled in --->
<cfloginuser name="#cflogin.name#" Password="#cflogin.password#" roles="role">
<cfset Session.id=cflogin.name />
<cfelseif getAuthUser() IS "">
<!--- User not yet logged in --->
<cfinclude template="loginForm.cfm">
<cfabort>
</cfif>
</cflogin>
<cfif getAuthUser() NEQ "">
<cfinclude template="logoutForm.cfm">
<cfabort>
</cfif>
<cfreturn true />
</cffunction>
</cfcomponent>
loginForm.cfm
<form method="post">
<b>login :</b>
<input type="text" name="j_username" size="24" class="champ" />
<b>password :</b>
<input type="password" name="j_password" size="15" class="champ" />
<input type="submit" value="Login" class="button" name="submit" />
</form>
logoutForm.cfm
<form method="Post">
<input type="submit" Name="Logout" value="Logout">
</form>
Added edit: I removed the session lock, as I think it is unnecessary.