Phone Shutting down when Idle?

[TygerX7]

Hi, I have a Samsung Galaxy PRO(GT-B7510L), with Froyo(2.2.2) I think, and I rooted it a few weeks ago(like 8 or 9), and all is good, but i've noticed that since a month ago, everytime its connected to WIFI, when it goes Idle, sometimes it doesnt turn on, i have to hold the power button for it to reboot, I dont know what could it be, is there a APP capable of such thing? anyways to find out? i got plenty of them, but I got Android Wall(stop apps from connecting to internet), and a Ad blocker for free apps, but I dont know what could be causing this,it gets annoying. Any help?