First let me tell you it’s not a fault. I did the very same thing when I first got this camera and started poking every button on it. I went to change the ISO while on a shoot and couldn’t, it had all locked up and I didn’t know what I’d done. Thankfully after 5 minutes of panicking I discovered that I had pressed one of the many Fn (function) buttons and locked the cursor buttons. Who knew!
Anyway, as I’m coming across these little frustrations I thought I’d post them here to help others that are bound to come across the same issues.