Literally, the hardware of your serial port has malfunctioned or not responded with a valid return to a query device function call. If the hardware has not physically failed, a hardware reset will usually fix the issue but typically this message has been noted to be associated with a physically damaged piece of hardware. In one case we had an incorrected wired null modem cable attached to a modem which would cause this error message until the cable was removed. A hardware reset was required even after the cable was disconnected.
I experienced this error on several IBM E232 servers. Could not find resolution and had IBM techs on site call into their super secret internal support area. Found that it's a known issue requiring a driver upgrade (driver upgrade was not available for public download).