IP Address Labelling Plug-in stopped working

I’ve been using the “Label your IP Addresses” successfully for a few weeks, but I can no longer get into the Slimstats > Settings > Add-ons tab. This is just showing as empty.

HTML shows:

<div class="clear"></div></div><!-- wpbody-content -->
<div class="clear"></div></div><!-- wpbody -->
<div class="clear"></div></div><!-- wpcontent -->

Not sure if it’s related, but when accessing the Settings > Maintenance tab, I see the following PHP error. The Maintenance tab seems to be working ok.

[Tue Dec 24 09:59:39 2013] [error] [client xx.xx.xx.xx] WordPress database error Duplicate key name 'all_idx' for query ALTER TABLE wp_xxx42_slim_screenres ADD INDEX all_idx(resolution,colordepth,antialias) made by do_action('slimstat_page_wp-slim-config'), call_user_func_array, wp_slimstat_admin::wp_slimstat_include_config, include('/plugins/wp-slimstat/admin/config/index.php'), include_once('/plugins/wp-slimstat/admin/config/maintenance.php'), referer: https://www.xxx.co.uk/wp-admin/admin.php?page=wp-slim-config&tab=7

Labelling plug-in seems to be working, but I can’t edit the settings. Tried deactivating and re-installing the add-on, but no joy.

https://www.ads-software.com/plugins/wp-slimstat/