Access 2000 ODBC table links

Hi,

there is a problem using Access 2000 as a frontend for pg data sources.
I make a new system DSN in the control panel and I leave blank the fields
for username and password. Then, I use this DSN to link some tables in an
Access MDB. So whenever I start this MDB and open some table, Access will
ask me for username and password. So far, so good, but: When I login in
this way for the first time, the username I give will be stored
somewhere, and you can never give another one. When I login for the second
time, after closing Access, I can change the username and password, but Access
will send the username from the first login, with the password of the current
login, and Postgres logs something like "password authentication failed for
user x".

So how can we use one frontend for different users?

Thanks,

Markus