Unfortunatly Nf is a somewhat buggy little app. I had problems snipe with exactly the same error msg but i was running osx. Resolved it by resetting my headset within the control panels and deleting my settings in NF and restarting it.... its been hunky doorey ever since!

from what the others have said, would suggest quiting ever app other than NF and making sure there are no conflicting apps causing problem! good luck!