Just to further confuse things
Just thinking this through in my head. When you set up wireless tethering, in effect your Incredible becomes a router. And I'll submit that it becomes a 802.11g router using the stock configuration.
Now, some of you (not me) have applied the hack to enable the Inc to act as a 802.11n client. It's important to differentiate between the two things here... (and forgive me if I'm over-dumbing this down) a client meaning that you use the Inc to connect to an existing WiFi network in order to connect to the Internet (normal use), as opposed to acting as a "router" to distribute the EvDO signal FROM the Inc TO other devices (tethering).
Now that I've got that out of the way... when you apply the hack to enable 802.11n, is it possible that the Inc isn't capable of acting as an 802.11n router? And that it can't drop into 802.11g mode? That would explain a lot.
While I'm at it, does a "hacked" Inc with 802.11n enabled succesfully connect to a router that only supports 802.11g and 802.11b, or does it lock it into "N-only" mode? Just curious... there are a lot of those routers out there yet (I still have a Linksys WRT54G at home, which doesn't support N) .