Tab key - Change in behaviour

Morning All,
I have managed to press a secret combination of keys and now my keyboard navigation shortcuts are behaving differently. For instance, the Tab key normally moves the active cell one to the right, now it moves the active cell a whole page to the right.

Pressing Ctrl + arrow key does not now move the active cell to the boundary of the active region etc.

Can anyone help...it's flippin' frustrating.
Thanks
SR08

Think I might have solved it....

In Tools, Options, Transition tab, I noticed that the Transition Navigation keys check box was checked. Unchecking the box has returned my keyboard to a more familiar set-up.

Still mystified how I did that unknowingly though...
Thanks
SR08