Thebigboss has issued a warning on their blog that the Jailbreakers who are enjoying Cydia Tweaks like SBSettings, winterboard, and every Tweak that needs Mobile Substrate should stay away from the upcoming iOS4.3.
The reason they said this is:
March 11th is the due date for the next iOS release. This is to support ipad2. As always, I give my standard warning not to update and wait for the jailbreak release. This time, I am giving some extra caution, however.
With 4.3 comes apple’s implementation of address space layout randomization (ASLR). In short, this will mess up the way mobile substrate works. You will need a new mobile substrate in order to use your favorite tweaks such as winterboard, sbsettings, bitesms, folder enhancer, etc. So you should definitely avoid 4.3 until an “official” jailbreak is released for it.
You should wait for the proper iOS4.3 Jailbreak to come out and the team of Cydia to work on the Stuff and get it fixed for you people. Thanks to BigBoss for reporting it on their web. We will let you know when ever the iOS4.3 Jailbreak is out and it is safe to Update. You can also prevent the accidental updates by following this simple guide here. Once you are done with the procedure and your iPhone will never ask you about the update and it will never update you iPhone/iPod/iPad even if you press update Accidentally.