Two days ago, SiriN1ght b3 was released to fix various issues with iMessage and video recording.
Some people now noticed a new bug: The keyboard doesn’t work anymore. The reason being is that because the Siri files are so big, some keyboards are removed upon installation.
To temporarily fix the keyboard, you have to change the keyboard to english. The keyboard will then work again in most Applications. If you still have issues in some Applications (ex. Cydia), you have to set your system language to english as well.
This issue should be fixed in SiriN1ght beta 4 or in the final release of SiriN1ght.