I doubt that LSWS version will affect this, it is a problem between PHP and xcache. You can use a cron job to kill those PHP process with ppid being "1".
Well, i'll test for you I have tried to kill old processes and LSWS has spawned new ones right away, mysql is also restarted just in case. Now i'm runing 4.0.16 and I'll need few days to check if new processes will be created and I will update this topic.
4.0.16 didn't made any difference I have killed all processes recompiled PHP to 5.2.14 and switched to 4.0.17 and it is fixed now. I see again process is spawned but it dies normally after few minutes. So I guess everything is back to normal.