postgresql-odbc vs. unixODBC

hi,

does anybody know what the differences are between postgresql-odbc
and unixODBC? because connection via postgresql-odbc work and
via unixODBC fails!

here some infos:

my /etc/odbcinst.ini:
---------------------
[PostgreSQL]
Description = ODBC for PostgreSQL (postgresql-odbc)
Driver = /usr/lib/psqlodbc.so
FileUsage = 1

[PostgreSQL2]
Description = ODBC for PostgreSQL (unixODBC)
Driver = /usr/lib/libodbcpsql.so
FileUsage = 1

my /etc/odbc.ini:
-----------------
[DB1]
Description = PostgreSQL
Driver = PostgreSQL
Database = DB1
ServerName = localhost
UserName = icp
Port = 5432

[DB2]
Description = PostgreSQL
Driver = PostgreSQL2
Database = DB2
ServerName = localhost
UserName = icp
Port = 5432

my /var/lib/pgsql/data/pg_hba.conf:
-----------------------------------
local DB1 uid md5
local DB2 uid md5

isql DB1 uid pwd => work fine
isql DB2 uid pwd => results in "[ISQL]ERROR: Could not SQLConnect"

any hints welcome!

cheers, rainer