When enabling v1.0.1 of the System Login Notify - I receive this error on my website front-end.
Fatal error: Cannot redeclare class JFormField in /home/farrells/public_html/v32/plugins/system/jat3/jat3/core/joomla/form/field.php on line 20
I have to disable the plug-in in order to get the site to load.
We have checked the code of this plugin and nothing seems doubtful.
It could be possible that due to some other extension installed at your site it is causing issue.