The last post being over half a year old, if anybody encounters this problem, it's indeed, as a previous user said, related to a wrong web.config or missing entries therein. You may change the code by appending the missing namespaces on top of the files, but this will be tedious: if you have this error, you'll have it everywhere.

The more recent version of the Starter Kit doesn't seem to have this issue. However, if you still encounter it, check whether your <pages> section inside web.config includes the following list (or similar, it's no problem if you have more entries in your list):

<namespaces>
    <add namespace="System.ComponentModel" />
    <add namespace="System.Data" />
    <add namespace="System.Data.SqlClient" />
    <add namespace="System.Drawing" />
    <add namespace="Microsoft.VisualBasic" />
    <add namespace="System.Globalization" />
    <add namespace="DotNetNuke.Services.Localization" />
    <add namespace="DotNetNuke.Entities.Users" />
    <add namespace="DotNetNuke" />
    <add namespace="DotNetNuke.Common" />
    <add namespace="DotNetNuke.Data" />
    <add namespace="DotNetNuke.Framework" />
    <add namespace="DotNetNuke.Modules" />
    <add namespace="DotNetNuke.Security" />
    <add namespace="DotNetNuke.Services" />
    <add namespace="DotNetNuke.UI" />
    <add namespace="DotNetNuke.Entities.Portals" />
    <add namespace="DotNetNuke.Common.Utilities" />
    <add namespace="DotNetNuke.Services.Exceptions" />
    <add namespace="DotNetNuke.Entities.Tabs" />
</namespaces>
 

Kind regards,

Abel Braaksma
Metacarpus