I get this problem too. Usually as I'm trying to do WILD, and the buzzing or vertigo feeling will come, but it just fades away.

For me, it fails because I'll be concentrating on something else, then I realize "Yay, it's working." and get excited. Everytime I attempt it though, I get closer and closer probably because it get's less exciting.

If this is your problem, just keep attempting it and eventually it will work.

This happens to me too, I don't understand it. Also it is normal to get no HI, personally I get no HS.[/b]
I don't get HS sometimes either.