[AccessD] Error in Access 2003 that I've never seen before

Perhaps I've just been lucky, but I have never seen this error before. I'm
trying to delete a bad record in a data table, and I get the message "The
search key was not found in any record." I clicked Help and it told me
"Error 3709 -- The error occurs when an ISAM Seek is being executed and
there are no matching values in the index."

The value in question was in an autonumber column that was the PK of the
table.

I tried a bunch of different things such as removing the PK and all indexes
but none of them worked. Finally I Saved As to a new table name (without the
indexes) and in the new table I was able to delete the bad record. So I
removed all the relationships to the bad table, renamed it, and renamed the
copy to the original name. Finally I reimposed all the relationships, and
now everything works properly again.

Since I am up and running again, I am fine I suppose. But I am most puzzled
as to why this error occurred in the first place. Anyone got any ideas on
this?

Arthur