corruption - toasted table

I think this cropped up before, but can't find it.

I've run into a problem in which I get "Missing chunk number 0 for toast
value 642223827"

I've tried reindexing the table and restarting the server, but the
problem persists.

I located an archive

"hunt down the damaged main row and update it's
toasted value with something fresh (there have been enough discussions
about it, you should find how to do that in the mailing list archives."

Can someone point me to some relevant FAQ, email etc?

Thanks

Jaime