So, here we are yet again! Took the computer in again today after it slowed down, froze a few times, then refused to start - at first. The first time it successfully restarted and after a lonngg wait, I could at least use the mouse. I had to change the size of the display so I had to shut it down and it took longer to restart, then I could not use the mouse at all. So, back to the store for 'fixing'; apparently it only takes a bump to upset something.
Will let you know what happens as I should hear from them by tomorrow.