The information you provided is a bit too general to give you much advise.
Can you explain what you mean when you say it "locks all passwords"? Does
your Radius daemon quit responding? Can you ping your Radius server?
Lastly, what happens to resolve the problem...does it go away by itself or
do you have to take action to "unlock the passwords" ?
Since you note that this happens at the same time each day, I'd be
suspicious of the machine you are using to run Radius. Check the crontab
file for anything scheduled at that same time, and/or watch the machine with
top to see if some mega-process is kicking in and simply crushing Radius
temporarily.
Damien