See the following thread in the mu fourms:
http://mu.wordpress.org/forums/topic.php?id=5018&page&replies=5
I corrected this on my site with two changes:
1. Change to wpmu-edit.php starting around line 28:
// original STEVE
// oupdate_site_option( "limited_email_domains", split( ' ', $_POST[ 'limited_email_domains' ] ) );
$limited_email_domains = split( "\n", stripslashes($_POST[ 'limited_email_domains' ]) );
foreach( $limited_email_domains as $domain ) {
$limited[] = trim( $domain );
}
update_site_option( "limited_email_domains", $limited );
} else {
update_site_option( "limited_email_domains", );
2. Change to wpmu-options.php around line 57 to make it a textarea:
<td><textarea name="limited_email_domains" id="limited_email_domains" cols='40' rows='5' style="width: 95%"><?//Steve Changed?><?php echo get_site_option('limited_email_domains') == ? : @implode( "\n", get_site_option('limited_email_domains') ); ?></textarea>
