Decided to take 5 mins off and read the manual and follow some of the examples to refresh my brain.
Tried typing "1234567890123456" to see what it did, i.e. whether it was an integer or a float.
I got to about '6' and the calc powered off as if it had lost battery power or I had OFFed it. (Batteries are fresh as of last night).
Turned on again and repeated test numerous times...but didnt reproduce the 'glitch'. Havent seen anyone else report this, but just in case.
I havent had any issue with the keys being too hard or different...strange. I put it down to Solar Flares for now.