very concerning, tables hopped from one database to another

I'm a bit anxious at the moment.  Things have been going just fine for a
couple months and this afternoon Something Bad (tm) happenend.

Summary.  I had 8 databases, I created another one for 9.  I started
psql and created a table, created a user, and granted permissions.  I
then did a \z to check up on things.  Lo and behold, I have 3/4 of the
tables from another database moved into here!  I disconnect, reconnect,
yep, still there.  I connect to the other database and those tables are
missing.  I'm absolutely positive that these tables were in 'hmzbook'
before this.  I triple checked and examined a dated pg_dump from a few
days ago and 'hmzbook' was correct.

$ psql -l
Password:
      List of databases
      Name       |   Owner
-----------------+-----------
 gayladb         | gayla
 hmzbook         | hmz
 horde           | postgres
 pg_auth         | postgres
 sendmail        | mailadmin
 sendmailexample | mailadmin
 template0       | postgres
 template1       | postgres
(8 rows)

$ createdb sysinfo_archive
Password:
CREATE DATABASE

$ psql -d sysinfo_archive
Password:
Welcome to psql, the PostgreSQL interactive terminal.
...

sysinfo_archive=# create table sysinfo ( timestamp timestamp default
'now', host inet not null, component varchar not null, node varchar not
null, identity varchar not null, value int8 default 0 );
CREATE

sysinfo_archive=# insert into sysinfo
(host,component,node,identity,value) values
('1.2.3.4','network','eth0','bytes in','1234');
INSERT 26374 1

sysinfo_archive=# create user mouse with encrypted password 'xxxx';
CREATE USER

sysinfo_archive=# grant select,insert on sysinfo to mouse;
GRANT

sysinfo_archive=# \z
     Access privileges for database "sysinfo_archive"
          Table           |       Access privileges
--------------------------+-------------------------------
 autthoughts              |
 guestbook                |
 guestbook_id_seq         |
 id_seq                   |
 iquotes                  |
 iquotes_id_seq           |
 ircfriends               |
 ircfriends_id_seq        |
 ircfriendsfriends_id_seq |
 picture                  |
 profile                  |
 sysinfo                  | {=,postgres=arwdRxt,mouse=ar}
 temporary                |
(13 rows)


What the heck just happened and short of dumping these tables out and
importing them back into the other database...

a) how can I fix this and
b) how can I prevent this from happening again?

Very concerned,
David