Você recebe este erro:
XML_E_BADCHARINSTRING - A string literal contained an invalid character.
O arquivo de configuração está danificado. Repare o .NET 2.0 executando sfc /scannow . Se isso não resolver o problema, copie o arquivo de configuração de C:\Windows\winsxs\amd64_netfx-machine_config_ocm_b03f5f7f11d50a3a_6.1.7601.17514_none_81fa0191bdd08961 para a pasta C:\Windows\Microsoft.NET\Framework64\v2.0.50727\CONFIG e substitua o arquivo de configuração antigo.
// Editar: Ok, aqui está a exceção que você recebe quando o aplicativo trava:
Nested exception -------------------------------------------------------------
Exception object: 000000000278f438
Exception type: System.Configuration.ConfigurationErrorsException
Message: Configuration system failed to initialize
InnerException: System.Configuration.ConfigurationErrorsException, use !PrintException 000000000278ee68 to see more
StackTrace (generated):
SP IP Function
000000000052C5B0 000007FEF8FCBEDD System.Configuration.ClientConfigurationSystem.EnsureInit(System.String)
000000000052E680 000007FEF8FCE699 System.Configuration.ClientConfigurationSystem.PrepareClientConfigSystem(System.String)
000000000052E6B0 000007FEF9057898 System.Configuration.ClientConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.RefreshConfig(System.String)
000000000052E6F0 000007FEF905747D System.Configuration.ConfigurationManager.RefreshSection(System.String)
000000000052E730 000007FEE75DD3C6 System.Configuration.ClientSettingsStore.ReadSettings(System.String, Boolean)
000000000052E7C0 000007FEE75AB30A System.Configuration.LocalFileSettingsProvider.GetPropertyValues(System.Configuration.SettingsContext, System.Configuration.SettingsPropertyCollection)
000000000052E890 000007FEE75AB113 System.Configuration.SettingsBase.GetPropertiesFromProvider(System.Configuration.SettingsProvider)
000000000052E920 000007FEE75DC7E3 System.Configuration.SettingsBase.GetPropertyValueByName(System.String)
000000000052E960 000007FEE75DC6AF System.Configuration.SettingsBase.get_Item(System.String)
000000000052E9C0 000007FEE75DC4FC System.Configuration.ApplicationSettingsBase.GetPropertyValue(System.String)
000000000052EA10 000007FEE75DC43F System.Configuration.ApplicationSettingsBase.get_Item(System.String)
000000000052EA70 000007FF00170934 Nexus.Client.Program.UpgradeSettings(Nexus.Client.Properties.Settings)
000000000052EAC0 000007FF00170470 Nexus.Client.Program.Main(System.String[])
StackTraceString: <none>
HResult: 80131902
-----------------
Total 12 exceptions
0:000> !PrintException 000000000278ee68
Exception object: 000000000278ee68
Exception type: System.Configuration.ConfigurationErrorsException
Message: Unrecognized configuration section system.serviceModel.
InnerException: <none>
StackTrace (generated):
SP IP Function
000000000052E580 000007FEF90AADF7 System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean)
000000000052E5C0 000007FEF8FCEAEA System.Configuration.BaseConfigurationRecord.ThrowIfInitErrors()
000000000052E600 000007FEF8FCBD2D System.Configuration.ClientConfigurationSystem.EnsureInit(System.String)
isto significa que a entrada de configuração system.serviceModel está faltando. Eu baixei o código, o compilei com o VS2012 e posso executá-lo sem problemas. Existe um arquivo chamado NexusClient.exe.config (na mesma pasta em que o exe está). O meu tem as entradas:
Verifique se você tem as mesmas entradas.