NI USB-Serial Adapter disconnects soon after plugging in

[kmuster93]

   My NI USB-232 is recognized in the Windows 7 "Devices and Printers" menu as 2 icons: "USB-232" and "NI USB-232/1 Communications Port (COM3)". But then the icon disappears after some time, anywhere from 1 second to 2 minutes, and the adapter is no longer recognized / I can't use it to communicate with the connected instrument. Unplugging, waiting, and plugging back in causes this to repeat.

   Has anyone come across this issue? Any ideas for fixing or troubleshooting this?

   I tried updating to NI VISA 15.0 and restarting, changing USB ports, disabling "USB selective suspend", and unplugging all other USB adapters in case it was a limited power issue (I'm using a desktop computer as opposed to a laptop, so it shouldn't have this issue, right?). These had no apparent change in how long it stays connected. It also didn't change whether or not an instrument was actually connected to the adapter. It does increase when unplugged for longer time. When not recognized but still plugged in, the serial end gradually gets warmer. I wouldn't think any current would be going through the adapter if it's not recognized, unless that's part of the problem.
   I could try re-installing NI-Serial in case it has to be installed while the new NI VISA is present, or updating NI Serial from 14.0 to 15.0. Please let me know if you have other suggestions.

[Minions]

Other than it sounding like you might have a faulty converter, just one other suggestion.

Make sure that your NI Device Monitor is set to: Run at Startup (Checked).  This way it does not constantly go checking for new equipment.