I believe the full text is:
[]Your post has been entered. In a moment you will be automatically returned to the forum.[/]
It's actually 2 strings, in two files. The first part:
[]Your post has been entered.[/]
Is in addpost.php as:
$ubbt_lang['POST_ENTERED']
The second part:
[] In a moment you will be automatically returned to the forum. [/]
Is in generic.php as:
Hope that helps.