Migrating file from the old gnumeric version to the current version

[Daniel Savard <daniel savard gmail com>]

I migrated my laptop from a old Redhat installation with kernel 2.4.2x
to Gentoo with kernel 2.6.10-r6.

I was thinking using the .gnumeric file will be straight forward, but
when I am trying to open a file, I am getting the following error:

Input is not proper UTF-8, indicate encoding !
Bytes: 0xE9 0x73 0x20 0x70

So, I had to convert my files from iso8859-1 to utf-8, which I did
with the iconv utility as follow:

iconv -f ISO8859-1 -t UTF-8 my_old.gnumeric > my_new.gnumeric

And now, when I am trying to open this file I am getting a message
saying the file format is not recognized.

What is going on? How am I supposed to convert my files?

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Daniel Savard