Serial comms failure after long time - can't open COM port I've been using an Arduino UNO to log data: it's queried by a LabView VI over a VISA connection. It'll happily sit there and log for days, but very occasionally one of the VISA functions will fail. 

After this, I can't open the COM port again (in LabView or elsewhere) and the only way to restore communication is to unplug and replug the USB cable. The Arduino hasn't crashed because I can see the other results of the program it's running working fine, but Serial comms are a gonner. 

Has anyone experienced this? Do you know if this is an Arduino problem, a Labview problem, a Windows problem? Or something else? 

I'm writing a minimum working example to try and catch this happening in the most simple code possible, but since the error usually takes several days to show up I can't tell you the results yet!
The assumption I am making is "VISA connection" is a PC operating VISA.
I have seen ports shut down on windows several times yet the same port works fine while in DOS.  My suggestion is try a different computer, that should narrow down your problem to which side of the connector is failing.