You probably changed the screen resolution.
Go into OS control panel for dispaly and change resoultion to something other than 150. Say 149 or 151. Weird huh?
Caps Lock key maybe...
thanks JJMack, been used to that one for about 8 years, so it was definitely not that. :-)
Thank you Curt Y , that helped! I had thought of all the things I might have changed on photoshop (which was none) but never thought about this being a new computer and that I had recently altered the font sizes.
I had to enter 149% like you suggested and that worked a treat! (definitely wierd)