Asp – Error with Subsonic 2.1

I'm getting very odd errors when compiling our Data Access library (all subsonic). Errors are

Error 35 The type name 'Web' does not exist in the type 'S3.DACL.System'    
      C:\Projects\S3\src\DACL\AspnetUser.cs 369 63 DACL

And

Error 37 The type name 'ComponentModel' does not exist in the type 
 'S3.DACL.System' 
C:\Projects\S3\src\DACL\AspnetPersonalizationPerUserController.cs 19 13 DACL

and they are on all of my subsonic generated classes.

I've got 2 projects — a Web project and then a class library called DACL. My web.config subsonic stuff is like this:

<connectionStrings>
  <add name="S3" connectionString="data source=ServerName;initial catalog=Cat1;
         user id=usenrame;password=password;" />
</connectionStrings>
<SubSonicService defaultProvider="S3">
  <providers>
    <add name="S3" type="SubSonic.SqlDataProvider, SubSonic" 
       connectionStringName="S3" generatedNamespace="S3.DACL"/>
  </providers>
</SubSonicService>

I had these error earlier tonight, but that was due to a type of the default provider parameter.

Anyone have any ideas why I am getting these errors? I'm desparate and have been banging my head against a wall for the last hour.