[Nikki Noo]

last week i done the latest software update on my s4, now i cant open up the text box to type at all. also my phone is lagging like crazy and sometimes the screen will go black on its own.
have tried clearing the keyboard cache and it didnt help

[B. Diddy]

Welcome to Android Central! Which carrier do you have? Do you know what the software update was for?

Try wiping the cache partition, which won't erase any personal data: http://support.t-mobile.com/docs/DOC-5744

[Nikki Noo]

im with telstra. i have no idea what the software update was for. i tried wiping the cache partition but it didnt make a difference... should i do a back up and restore?

[B. Diddy]

Not yet. Do you have an SD card inserted? A corrupt card can cause various problems. Unmount it (in Settings>Storage), remove it, and reboot.

[Nikki Noo]

i dont have an sd card in the phone...

[B. Diddy]

Ok, try booting into Safe Mode, which prevents all 3rd party apps from starting. If the problem goes away in Safe Mode, then you know that something you installed is causing the instability--the challenge then is to pinpoint the culprit. Sometimes you have to uninstall apps one by one until the problem goes away. Safe Mode instructions are also in that other link I shared above.

[Nikki Noo]

i tried this also, still nothing. and whenever i go into language and input and then if i look under keyboards and input methods, samsung keyboard is selected, but it isnt highlighted and if i try and go into the keyboard settings, the screen goes black and stays black...

[B. Diddy]

At this point, you may want to do a full factory reset. Make sure all of your data is backed up or synced beforehand.