Today, I've installed the new 1.5 version of this plugin but it could not be activated. The error is:
Fatal error: Cannot redeclare message() (previously declared in /public_html/wp-content/plugins/dmsguestbook/admin.php:3459) in /public_html/wp-content/plugins/statpress-visitors/statpress.php on line 90
Both plugins have a function message().
After renaming the conflicting function to StatPressV_message() it activates without problem.
Maybe you can look at this?