Errors when starting Toad: "Exception has been thrown by the target of an invocation" and "Invalid window handle". (4224590)

The following errors occurs at startup / launch of Toad:

Error 1:

System.Reflection.TargetInvocationException:
Exception has been thrown by the target of an invocation.
Stack trace:
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)

Error 2:

System.ComponentModel.Win32Exception
Invalid window handle.
Stack Trace:
   at MS.Win32.UnsaeNativeMethods.CreateWindowEx(Int32 dwExStyle, String lpszClassName, .....

Error 3:

Failed to open the settings for module DB2 due to error  Attempting to Deserialize an empty stream.  Reverting to defaults.