The iPhone Dev Team has been fervently working away on a number of bugs that were reported on the first beta tester version of RedSn0w for iOS 4.2.1. The latest beta 3 version named RedSn0w 0.9.7b3 fixes a number of things including third party app crashing, embedded videos, etc.
In an update to their redsn0w blog, the iPhone Dev team writes,
” The third beta is now available (testers ONLY please!). This version extends the fix made in beta2 over to the non-GUI programs too (like the daemons that handle media content). That should cover things like Facetime, Winterboard themes, and embedded videos in iTunes. If you had trouble using the usbmuxd in previous betas, please wait until we incorporate that into redsn0w itself (i.e. don’t bother trying this beta3, just wait for the integration).”
An earlier beta 2 version had fixed the native app crashes. Although this won’t be the last of the beta releases, you can still check out if you are a seasoned jailbreaker who can manage all the eventualities. Otherwise, it is best advised to stay put until a general release is announced.