If you are one of the unfortunate ones, that experiences your device stuck in an endless hung state after installing an app from cydia. This happens when a bad/corrupt package is installed and does not play nice with the device.
To fix the device that is hung trying to respring, simply download and install iFunBox. ( http://www.i-funbox.com/)
Next connect your device to your laptop/pc, open ifunbox, then navigate into the following folder.
/Library/MobileSubstrate/DynamicLibraries/
Find the last package you tried installing that caused the respring to hang and delete those files, then power cycle the device and it will be back to normal.