Earlier today, the iPhone-Dev team released Redsn0w 0.9.10b2 which was to fix issues with launchctl from b1. However, it became apparent that running this new version of Redsn0w on top of an already jailbroken device would cause any apps that used MobileSubstrate to stop working. If this has happened to you, you can simply reinstall MobileSubstrate and reboot your device, otherwise Redsn0w 0.9.10b3 will fix the issue for you as well.

Remember, when running b3 on top of an already jailbroken device, be sure to uncheck the "install cydia" option. 
Redsn0w 0.9.10b3 fixes a problem where re-running redsn0w over an existing jailbreak would cause MobileSubstrate-based apps to stop running until MS was installed again.  Now you can re-run the redsn0w jailbreak step without worrying about that (but still remember to de-select the “Install Cydia” option if it’s already installed).


Redsn0w 0.9.10b3 - Win
Redsn0w 0.9.10b3 - OSX