Dev Team first released the RC10 version of RedsnOw 0.9.6, but they pulled it and released RC11 now with a fix. Dev Team has pushed out RedsnOw 0.9.6RC11 adding an option to enable custom boot animations after the untethered iOS 4.3.1 jailbreak with it. RedsnOw 0.9.6RC11 is available to download for both Windows and Mac OS X. The last day, SnOwbreeze 2.5.1 was released adding the same feature along with some other fixes.

Download Redsnow 0.9.6 RC11

You could jailbreak iOS 4.3.1 untethered using RedsnOw 0.9.6RC11 using the guide given here(Just replace RedsnOw 0.9.6RC9 with RC10).

Download RedsnOw 0.9.6RC11 for Windows from here

Download RedsnOw 0.9.6RC11 for Mac OS X from here