How can SerialPort.set_ReadTimeout throw IOException { NativeErrorCode = ERROR_OPERATION_ABORTED }?

After sending a message out a SerialPort to a device, in preparation to read back its response, I tried setting the ReadTimeout and got back a rather oddball error:

System.IO.IOException was unhandled
  Message="The I/O operation has been aborted because of either a thread exit or an application request.\r\n"
  Source="System"
  StackTrace:
       at System.IO.Ports.InternalResources.WinIOError(Int32 errorCode, String str)
       at System.IO.Ports.InternalResources.WinIOError()
       at System.IO.Ports.SerialStream.set_ReadTimeout(Int32 value)
       at System.IO.Ports.SerialPort.set_ReadTimeout(Int32 value)

There are no other threads accessing the SerialPort, and no event handlers regi开发者_如何学运维stered with it (which I hope would rule out interference from the implicit thread behind the port).

In any case, though, it just seems weird to me: how can SetCommTimeouts fail with ERROR_OPERATION_ABORTED?