serious connection problems

I have have 2 databases running on my system ("intranet" and
"tempdata"). I can access "intranet" without problem but I cannot
connect to "tempdata" anymore. If I create a new database let's say
"tempdata2" I can't connect to it, too.
"intranet" and "template1" seem to be the only databases I can connect
to.
Restarting PostgreSQL or dropping and creating the database does not
help.
Does anybody have an idea? I am using PostgreSQL 7.03
Permissions are ok and haven't changed. The problem occurred after 1
month of 100% availability.

kshopd@a:~/backup > psql tempdata
psql: pqReadData() -- backend closed the channel unexpectedly.
        This probably means the backend terminated abnormally
        before or while processing the request.

kshopd@a:~/backup > psql intranet
Welcome to psql, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

intranet=> \q


    Hans