I upgraded my php version from 5.3.8 to 5.4.5 and eversince I am getting the warning "Illegal string offset 'action' " on the settings page an on the blogg itself. The plugin still works, but with these warnings it is not usable.
This seems to be caused by trying to use a variable as an array that is not an array anymore. For example on line 323
if ($action_val['action'] == 'i')
In the previous php version this caused no warnings, but it seems that since version 5.4, they have made some changes to array handling.