First off I tried to search and didn't find anything on this, has this happened to anyone?
During text messaging, out of nowhere my phone will not go into landscape mode. I have everything updated and the phone has worked flawlessly until this happened.
I can go into landscape mode just fine for everything else, just not for text
I have had this happen to me a few times. Although after a battery pull it went back to working in portrait for me. I am using the Verizon official update, not the leaked one, so I have no idea. But I agree, it's really freaking annoying when it happens.
If a battery pull did not fix the issue, maybe its a conflict with an app. Try uninstalling any third party apps. If you don't have any third party apps, then I would say its time to backup your data and do a wipe.