I want to allow my customers to be able to sign into my force.com site (via authenticated website access) and allow users to view and edit certain fields related to them (i.e. email &phone details etc).

Now the first issue I have is that there are duplicate details held on the customer, one in the Contacts object and another in the Users table (when they have authenticated website/customer portal) access. How can I have both records sync'ed when they update their details?

The second issue is I've attempted to create a simple page with a standard Contact controller to display the contact details to the user but this has failed, the page returns...

Error: Insufficient Privileges

I know its not because the privileges are not setup correctly because as soon as I take out outputText line from the following text, the page loads

Page:

<apex:page showHeader="false" title="My Details" standardController="Contact">
<apex:composition template="{!$Site.Template}">
<apex:define name="body">  
...
<dt>Name</dt>
<dd><apex:outputText value="{!Contact.Name}"/></dd>
....