Help --> connecting to postgresql 8.1

Dear List of PgAdmin III,

Unfortunatelly i have a problem with connecting to (localhost)
postgresql whitch occures with many clients.
I don't really know that who could solve this problem.
I always get an error message telling that authentication failed - with
some other clients, only: could not connect to postgresql.

I could not find anything usefull in
#mcedit /var/log/postgresql/postgresql-8.1-main.log and nothing was
recorded about my tries.
I have tried searchhing in the archive of this forum, FAQ, but it was
barren :(. Are there any missing components of postgresql.
What do you thing i should do, look for?

(OS: Debian GNU/Linux SID, pgAdmin III v1.2.2 Nov 29 2005)

--

Tisztelettel: / Grüße / Yours sincerely,
Andrew Toth
BMF-NIK, BMF-Humán
tothaa(at)freestart(dot)hu
MSN: tothaa(at)msn(dot)com
ICQ: 311-837-92