ERROR 126 (HY000): Incorrect key file for table

[Jean-Paul Le Fèvre]

I'm stuck with "ERROR 126 (HY000): Incorrect key file for table" ...

I've a production database located on one machine.
On a regular basis I run mysqldump to get the current content into
a sql file.

I have a backup linux machine hosting the backup database. Using the
generated sql script I create a copy of the tables.

Unfortunately, at this point, this procedure fails. It used to work
some weeks ago but, now, the backup copy no longer works for 4 tables.
But it is still successful for the 20 others.

Using "myisamchk -r" does not help since, once repaired, the tables have
not the correct number of rows.

I've upgraded the server from mysql-5.0.4 to mysql-max-5.0.13 but it has
no effect. The OS is 2.4.20 with glibc 2.2.

I've tried "select * into outfile" followed by a "load data infile"
but the problem remains ("ERROR 126 ...")

However the same procedure used on another computer works correctly as
expected. This computer has a mysql-max-5.0.12 version running on
a linux 2.6.9 with a glibc 2.3.

I've googled a lot, perused the forums but without finding something useful.