I have been using Word for 15 years - and consider myself to be close to
being a power user. However this error has be preplexed and confused.

If I change single formatting, doesn't matter if high highlight the text or
just keep the pointer in single space, it changes all the text in the
document to that.
For example, if I want to have one line centered, it will center the whole
text.

The even STRANGER thing is - that if I press undo - it will change all the
other text to previous position, expect the text I want to change.
This makes me think that this is some sort of setting that I've never heard
of.

Please help....