With the iPhone OS 4.0 jailbreak, some users have been facing unexpected SMS and data issues. MuscleNerd of the iPhone Dev-Team posted about an update to redsn0w which mainly addresses these issues. Please note that this is still a developer release and that you will need a registered developer UDID to get past activation.
Here’s what MuscleNerd had to say about it:
For those 4.0b1 JB devs with SMS or data issues using redsn0w, the update at https://is.gd/buMgi should fix (restore 1st!)
For those JB app devs who experienced SMS or 3G data failures, the new 0.9.5b2 download at the bottom of this page should clear things up. You’ll need to do a fresh restore to stock 4.0b1 before applying the new beta redsn0w update.
Like all previous versions of redsn0w, 0.9.5b2 also remains the same when it comes to the method used for using the application. Chances are, if you’re an experienced developer, you’d probably get rid of these issues using the latest redsn0w. For novice and regular users, our advice is to stay away from OS 4.0 beta unless there is a final release and a complete, bug-free solution.