It happened last night. I was using a private header ripped from a pokemon game, haven't used the header for other games, just MH4. The last time I used it was downloading LDC for mh4 like a month ago. Tried to go online last night and I was benned. Gateway emunand 9.5, sysnand 9.0.
According to your answers, you said you did use a public header a month ago for dlc. My theory is Nintendo must have kept a log on you and ban you after going through their list of logs.