Most likely you have an incompatible tweak. If you have Substrate Safe Mode installed (comes with SBSettings if you installed that as well), you can put your device into Safe Mode and delete the incompatible tweak using Cydia. Otherwise, you'll most likely have to restore and rejailbreak to make sure all the components are removed from your device.
I just want to add a slight correction, here. With apologies, but Mobile Safe Mode is auto-installed if you install MobileSubstrate. MobileSubstrate is a tweak written by Jay Freeman (aka saurik, owner of Cydia) to allow various tweaks (SBSettings being one of them) a way to "hook" into the functionality/operating system of the iDevice.
Saurik developed Mobile Safe Mode as a feature to allow for an easy way to get into safe mode (a lot of people were crashing their iToys, but hadn't installed a way to get INTO safe mode - so they couldn't get out of the crash to fix it, so they were stuck with the crash ... which usually ended up with them having to restore. Now that the tweaks that require MobileSubstrate to run (which are the ones that would cause the crashes 99.9% of the time) also auto-install Mobile Safe Mode - many, many people can fix crashes versus having to restore.
As most tweaks that work with the file system of the iDevice require MobileSubstrate to work, saurik added the Mobile Safe Mode as an auto-add when MobileSubstrate is downloaded (it's by default - you can't get one without the other). MobileSubstrate is listed as a dependency on many tweaks, including SBSettings, so it gets loaded along with the tweak. But, you can install it separately and you don't have to install SBSettings to have it - many other tweaks will install Mobile Substrate as a condition of their download/install.
Pontificating over. This is just so's you know....
Marilyn