Device won't wakeup from power button

I used a Navigator app that prevents my device (Galaxy S2 with Cyanogenmod) from turning the screen off while plugged in. But at some point I could no longer wakeup the device screen with the power button anymore. The only thing that wakes up the device screen is to plug it into a USB charger. This behavior continues even after uninstalling the app. The device is not turned off, it's just the screen wakeup from the power button that stopped working. I assume that the app overwrote some settings. I couldn't get any help from developers of app. Thanks for any help!