I'm unable to reproduce your effects.
Check to make sure you have appropriate access within the channel to match your script.
I "redid" your this to make:
on *^:TEXT:!setevent*:#:{
if ($nick isreg $chan) || ($nick isvoice $chan) { halt }
else {
set %event $2-
msg $chan The current event has been set to : %event .
}
}
on $^1:TEXT:/^!(event|events)/iS:#:{
if ($nick isreg $chan) { notice $nick Voice or higher only. | halt }
else { notice $nick 8,2The event today is %event . }
}