[SM-PLUGINS] chpasswd problem on ubuntu - "No such file or directory"

[Matheus L. <gui...@gm...>]

I have installed the change_passwd plugin, but it doesn't work. So a tried
to run the chpasswd as below:

$squirrelmail/plugins/change_passwd# ./chpasswd

but it return the message:
bash: ./chpasswd: No such file or directory

Its importante to show the file permissions:
$ls -la chpasswd
-rwsr-x--- 1 root www-data 9873 2008-08-07 17:56 chpasswd

The group "www-data" is the group used by the apache, but I belive that's
not a problem, because I'm trying to use the command as root first.

Then, I send this same file to another server "not a ubuntu server", that is
a slack. And tried to run it.
And wokrs perfectly.

So, whats the problem, how can I fix it?

PS.: If its importante the server is a 64 bit ubuntu.