Crash: backup / restore

PGAdmin hangs when dumping / restoring a database. I can get to the 
screen that has the pg_dump / pg_restore command, but after that screen 
is displayed there is no progress, and only thing I can do is kill the 
program. (the file dumped to is created but it is empty).

I thing the bug is related to my pg_hba.conf, relevant lines:

local   all         all                               trust
host    all         all         127.0.0.1/32          trust
host    all         all         xxx.zzz.0.0/16           md5

I use user "akaariai" which has no password and which is both database 
superuser and my local linux user.

My PGAdmin connection is set up as follows:
name: localhost
host: localhost
port: 5432
maintenance_db: postgres
username: akaariai
store password checked, restore_env checked. Nothing else set, that 
means also no password set. I can open the connection without any errors.

The command PGAdmin is trying to run when backup is requested:
pg_dump --host localhost --port 5432 --username akaariai --format ...

If I run the command manually, the command asks for password. If I run 
the command without "--host localhost", there is no password prompt. 
Could it be that PGAdmin doesn't expect the server to ask password?

Also, if I remove the host=localhost from pgadmin connection 
configuration (leaving host blank), I can backup any DB without errors.

I am using ubuntu 10.04, apt installed postgresql 8.4.5, apt installed 
pgAdmin, version: 1.10.2 rev 8217.
 - Anssi