Note: This is a solved problem, but I just spend 4 hours at this issue, so I wanted to share the solution.
When I attempt to access a WCF service, the service never responds, and the event log shows the following:
An unhandled exception occurred and the process was terminated.
Application ID: DefaultDomain
Process ID: 3180
Exception: System.Runtime.Serialization.SerializationException
Message: Unable to find assembly 'System.Data.SQLite, Version=1.0.66.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139'.
StackTrace: at System.Runtime.Serialization.Formatters.Binary.BinaryAssemblyInfo.GetAssembly() at System.Runtime.Serialization.Formatters.Binary.ObjectReader.GetType(BinaryAssemblyInfo assemblyInfo, String name) at System.Runtime.Serialization.Formatters.Binary.ObjectMap..ctor(String objectName, String[] memberNames, BinaryTypeEnum[] binaryTypeEnumA, Object[] typeInformationA, Int32[] memberAssemIds, ObjectReader objectReader, Int32 objectId, BinaryAssemblyInfo assemblyInfo, SizedArray assemIdToAssemblyTable)
at System.Runtime.Serialization.Formatters.Binary._BinaryParser.ReadObjectWithMapTyped(BinaryObjectWithMapTyped record) at System.Runtime.Serialization.Formatters.Binary._BinaryParser.ReadObjectWithMapTyped(BinaryHeaderEnum binaryHeaderEnum) at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.Run() at System.Runtime.Serialization.Formatters.Binary.ObjectReader.Deserialize(HeaderHandler handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage) at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream, HeaderHandler handler, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage) at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.DeserializeObject(MemoryStream stm) at System.AppDomain.Deserialize(Byte[] blob) at System.AppDomain.UnmarshalObject(Byte[] blob)
Solution In my case, the problem ended up being a simple incorrect database path. However, the error message in no way reflects the actual cause, so YMMV.
The reason the "bad connection string" exception didn't make it to the event log seems related to this KB article. If the connection string isn't your problem, then your best course may be to follow the steps in this article, which will cause IIS to write exceptions to the event log.