I don't want to uduly alarm, but you might want to get checked for strokes. My stepdad had some mental problems that started suddenly too. He is 67. When Altzheimer's was ruled out, we found out that he'd had some small strokes and is being treated now and is much better.
I didn't realize that strokes could result this way; I'd always thought it only caused physical probs., but no physical probs for him.
You might want to get an MRI.