could not open relation...No such file or directory

We are using postgresql 8.2.17 on Gentoo

Our postgresql database stopped working with the error
ERROR: could not open relation 1663/26468499/26470404: No such file or
directory

After one minute of these errors on every statement run we had what
looks like a memory failure:
Dec 22 16:37:44 localhost kernel: [279820.425911] postgres invoked
oom-killer: gfp_mask=0x280da, order=0, oom_adj=0
Dec 22 16:37:44 localhost kernel: [279820.425917] postgres cpuset=/
mems_allowed=0
Dec 22 16:37:44 localhost kernel: [279820.425922] Pid: 26209, comm:
postgres Not tainted 2.6.32-gentoo-r7 #12

We cannot connect to the database using psql as it gives the could not
open relation error. We ran fsck and did not find any problems. I
searched through google and found suggestions such as reindex, but we
can't connect to the db. We also can't take a backup of the database as
pg_dump gives the same error.

This is our production database and crashed at the end of the day. If
possible, I would really not like to lose a full days work by restoring
yesterdays backup.

Thanks
Sim