Exception from AddExternalReference

I'm evaluating V4.0 with the Languages Add-On (very impressed so far!) but am getting the following exception when attempting to add a reference to a DLL in the test application (this occurs with one of our DLL's and also with a third-party DLL):

Unable to read beyond the end of the stream
at System.IO.__Error.EndOfFile()
at System.IO.BinaryReader.ReadByte()
at System.IO.BinaryReader.Read7BitEncodedInt()
at System.IO.BinaryReader.ReadString()
at k.a(BinaryReader A_0, w A_1)
at k.a(BinaryReader A_0, ad A_1)
at k.c(BinaryReader A_0)
at k.a(BinaryReader A_0, ai A_1)
at k.b(BinaryReader A_0)
at k.a(BinaryReader A_0)
at k.d(BinaryReader A_0)
at k.d(BinaryReader A_0)
at k.b(DateTime A_0, String A_1)
at k..ctor(Assembly A_0, String A_1, String A_2, String A_3, Boolean A_4)
at k..ctor(Assembly A_0, String A_1, Boolean A_2)
at ActiproSoftware.SyntaxEditor.Addons.DotNet.Dom.AssemblyCodeRepository.a.a(c A_0)
at ActiproSoftware.SyntaxEditor.Addons.DotNet.Dom.AssemblyCodeRepository.a.a(c A_0)
at ActiproSoftware.SyntaxEditor.Addons.DotNet.Dom.AssemblyCodeRepository.Add(String assemblyName, DotNetProjectResolver projectResolver)
at ActiproSoftware.SyntaxEditor.Addons.DotNet.Dom.DotNetProjectResolver.AddExternalReference(String assemblyName)
at TestApplication.QuickStart.DotNetReflectionForm.ExecuteAppAction(AppAction action) in C:\\Program Files\\Actipro Software\\SyntaxEditor\\v4.0.0230\\TestApplication-CSharp.Net20\\QuickStart\\DotNetReflectionForm.cs:line 596

Our DLL was built with VS 2005, the third-party DLL with VS2003. Let me know if there's any further information that will help.