MuscleNerd of iPhone Dev-Team has just posted about an update of Redsn0w which fixes SMS and data issues that some of you may be having with iPhone OS 4 jailbreak.
Official change log of Redsn0w 0.9.5b2 (beta 2) is as follows.
MuscleNerd For those 4.0b1 JB devs with SMS or data issues using redsn0w, the update at http://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 link) should clear things up. You’ll need to do a fresh restore to stock 4.0b1 before applying the new beta redsn0w update.
Instructions to jailbreak iPhone 3G on iPhone OS 4 Beta using Redsn0w 0.9.5b2 are exactly similar to the last release. Please read all the instructions posted here carefully before upgrading your phone to iPhone OS 4 Beta.