Scary behavior after power failure

We had a power failure (and a UPS failure) on our database machine. It's
back up now but some spooky stuff is happening. Here's an example:

(Names changed to protect the guilty.) First, the table:

---

CREATE TABLE foo
(
id SERIAL PRIMARY KEY,

bar INT NOT NULL REFERENCES blah (id),
...

UNIQUE(bar, baz, blee)
);

---

Now take a look at this:

---

pdm=# select * from foo where bar = 5;
id | bar
----------+------
13495206 | 5
13495206 | 5
(2 rows)

(Me: huh? How is that possible? The "id" column is the primary key!)

xxx=# delete from foo where id = 13495206;
DELETE 1

xxx=# select * from foo where bar = 5;
id | bar
----------+------
13495206 | 5
(1 row)

xxx=# delete from related_purchases where id = 13495206;
DELETE 1

xxx=# select * from foo where bar = 5;
id | bar
----------+------
(0 rows)

---

Is there any way I can "sanity check" the remaining tables for craziness
like this?

-John