Airport Express Tiger/Lion internet & common connections problems

I have problem with my Airport Express last time. Then I reset it and try to setup again. But now it stay difficult.

First of all, I use old Airport Utility and Airport Setup Assistant to make network and I can't find suitable because newest one (for Lion) eliminates my old Airport Express.

Some time it determines Airport Express, sometime No. Some time I make Network but then I try to connect to it system tells "wrong login or password".
Most often, the system issues an error in determining the Airport Express. Sometime reccomend to make bridge for internet connection.

I fill like I hit in gap between old and new era.