I think the issue here is that assemblyinfo.cs has a bunch of these:
[assembly: InternalsVisibleTo("DotNetOpenAuth.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100AD093C3765257C89A7010E853F2C7C741FF92FA8ACE06D7B8254702CAD5CF99104447F63AB05F8BB6F51CE0D81C8C93D2FCE8C20AAFF7042E721CBA16EAAE98778611DED11C0ABC8900DC5667F99B50A9DADEC24DBD8F2C91E3E8AD300EF64F1B4B9536CEB16FB440AF939F57624A9B486F867807C649AE4830EAB88C6C03998")]
[assembly: InternalsVisibleTo("DotNetOpenAuth.Core.UI, PublicKey=0024000004800000940000000602000000240000525341310004000001000100AD093C3765257C89A7010E853F2C7C741FF92FA8ACE06D7B8254702CAD5CF99104447F63AB05F8BB6F51CE0D81C8C93D2FCE8C20AAFF7042E721CBA16EAAE98778611DED11C0ABC8900DC5667F99B50A9DADEC24DBD8F2C91E3E8AD300EF64F1B4B9536CEB16FB440AF939F57624A9B486F867807C649AE4830EAB88C6C03998")]
etc.
Of course, if you follow the instruction here
http://www.dotnetopenauth.net/developers/contributing/quickstart-environment/ (like the, OP did, and by the way both a publickeyfile and keypaircontainer are prescribed to be used in this doco) you are going to change the public key, so all theses InternalsVisibleTo become invalid. No wonder it has accessibility problem afterwards.
I'd still very much like to know a working solution to this problem...