Fix Crashed Apps On Jailbroken iDevice By Entering iDevice into Safe Mode: Many users who have jailbroken iPhone, iPad or iPod touch may have faced crashes while using 2 or more app simultaneously. Mobile Substrate package comes with jailbreaking puts the device in safe mode before an iDevice can crash completely.
There are three ways to put your iDevice in Safe Mode.
1) Restart your iDevice by holding down the home and power button simultanously until the phone restarts. When the Apple logo is displayed, press and hold down the volume up button. This temporarily disables all Cydia tweaks, and launches the device in safe mode.
2) Second method which is to download and install Safe Mode Launcher from Cydia. This app is free, and does exactly what its title implies with the tap of a button.
3) Third method to enter safe mode is using SBSettings. If you have SBSettings installed on your device, all you have to do is hold down the power button and select safe mode.