Case sensitivity problems with user name

Hi.

I have a little problem with user names and Postgres commands.

Due to quirks in corporate account management using ADS, some user names
come out as, say, Mickey when you log into Linux instead of mickey.
This unfortunate user tries to run Postgres commands and gets for
instance:

$ psql

psql: FATAL: database "Mickey" does not exist

$ id

uid=123456(Mickey) gid=...

$ pg_dump >dump.out

pg_dump: [archiver (db)] connection to database "Mickey" failed: FATAL:
database "Mickey" does not exist

$ psql mickey mickey

Welcome to psql 8.3.6, the PostgreSQL interactive terminal.

. . .

I have set up pg_hba.conf with lines like

local all all trust

host all all 127.0.0.1/32 trust

I tried modifying pg_ident.conf but couldn't get any results.

When I try going into psql as user postgres to change the user name, I
get this problem:

postgres=# alter user mickey rename to Mickey;

ERROR: role "mickey" already exists

What can I do so that the default user is accepted? I would like the
user to be able to just type:

$ psql

and get in successfully.

Any help would be appreciated.

-Will