Usermin is getting stuck. Log shows "too many children"

Hi, I have a server running Usermin and recently it started having some problems, the process is not responding after a while and I have to access the Usermin configuration, stop the process and start it again. After that Usermin works good until it gets stuck again and I have to do it all over again. I search the logs and found this when the process gets stuck too many children (51 > 50). Can someone tell me how to solve this problem? Thanks in advanced!!