I can't log in

Hi everybody, I'm new here :).
I need some help because I installed postgresql in ubuntu dapper drake with no problems (i did with the repository of ubuntu). The postgres version that i installed is 8.1. I can log in postgres with the psql client with no problems. But when i try to connect to the server from pgadmin3, pgadmin tell me something like "there's an error with the password authentication of the user "postgres". I tried many options, Y modified the configuration file of the server to give at "postgres" user a "trust" authentication from the local machine, and still it told me the same (i have pgadmin in the same machine).
But the problem isn't just with pgadmin. I tried to connect with netbeans 5.5, and the same error raised. What can I do? :S
PD: Sorry for my poor english. I'm learning it.

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