Yesterday, I implemented a PM flood control system to solve some problems of spambots using PMs to advertise their site.
Problem is, I misread the description of that setting:
QUOTE
Enter the number of minutes users must wait between sending PMs.
I misread 'minutes' as 'seconds' so at that point, users need to wait for 30 minutes (o_O ) in order to send another PM.
I changed that setting to 1 minute from now on. Sorry for that.