I don't know thats strange
I create an ad-hoc network from my ubuntu laptop often because I don't have a wireless router at the moment.
I don't use any security on the ad-hoc network, I live out in the middle of the woods, so no one around to steal my internet.
my n810 sees it right away and connects. haven't had any problems with it.

although as a side note a friends laptop that runs vista can almost never connect to the ad-hoc network even though it can see it. good ol' vista.