Corrupt DB

Greetings,

I am running Postgresql 8.0 on "Linux xxx 2.4.18-14 #1 Wed Sep 4 12:13:11
EDT 2002 i686 athlon i386 GNU/Linux" and while loading data my program
received:

DBD::Pg::db do failed: server closed the connection unexpectedly ...

Now I can't access any data in the DB, not even the \d command:

mydb=# \d
ERROR: could not identify an ordering operator for type name
HINT: Use an explicit ordering operator or modify the query.

I tried vacuum:

mydb=# vacuum;
ERROR: could not open relation 1663/12649295/16396: No such file or
directory

What would be the best way to fix this?

How would I determine what caused the corruption and prevent it from
happening again?

Thanks for any assistance,
Drew.