Stops receiving data


I've noticed that after I leave this running for a few hours, that the SerialDataReceived event stops getting fired, and thus no data is recorded. I've added in several debugs and added a handler on the ErrorReceived event, but so far none of these have been triggered.
I'm a bit stumped at the moment whether it is the EnviR unit (white data cable plug) is no longer sending or that the .NET serial port interface is failing somewhere. I've read several sites that indicate that the .NET serial port classes are not implemented particularly well, so this may be the cause.