DB Access Works In Debug But Fails When Hosted

I have written a intranet page that writes some info into a sql database, basically following the 'SQL Server 2005 Express for Beginners' video.
When I debug the application from within 'Visual Web Develop 2005 express' it works fine entries are entered into the DB and I can then edit the db using the admin page.
But when I host the site using IIS I doesn't work, submissions to the database seem to fail I can see the DB in the admin page but if I try to edit them or delete them it fails.

What could I doing wrong could I be missing a setting in IIS? Any ideas??
Here's my webconfig if that helps at all: 
 <?xml version="1.0"?>
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
    <connectionStrings>
        <add name="studentprofilesConnectionString1" connectionString="Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|studentprofiles.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient"/>
    </connectionStrings>
    <system.web>
        <roleManager defaultProvider="AspNetWindowsTokenRoleProvider" />
  <compilation debug="true" defaultLanguage="c#" /></system.web></configuration>