Cameras: I installed Nikon nx-i 6 months ago, all of a sudden shows program not responding. How can I correct this?

I would uninstall all Nikon software.  Next restart the computer and only then reinstall everything.  It's important to not connect the camera to the computer prior to installing all the software.  Also, make sure that you go to Nikon's website and download all the most recent versions.  Installing from the supplied CD/DVD that came with the camera is always a bad idea since software on it is likely to be outdated.

I've run into a few situations where I've gotten the "Program not responding" error.  Sometimes simply waiting does the trick.  It is possible that the program is busy doing something like downloading and installing an update.

Cameras: I installed Nikon nx-i 6 months ago, all of a sudden shows program not responding. How can I correct this?

either re-install the software , if that doesnt fix it , its your cable or camera .

Either one or more files related to the program got deleted or is corrupted or there was a hardware change in your computer that the program depends on. Either way, the most obvious solution is to reinstall. If a reinstall does not work then a dependency might be missing. Check system requirements again to see if your computer is up to it. If you can't find what's wrong, download the latest version of the program, install that and see if it works. If it still doesn't, call Nikon.

You can try rebooting the computer and if that does not work, reinstall the program

Uninstall then reinstall. If you had an external drive plugged in, and now you don't, some poorly written programs (Nikon's strong suite isn't programming for the masses) will become inoperative if the drive isn't there.