Shift key problem

hey guys i have used photoshop for a few years now and have never had any problems, however i was on a friends computer the other day and went to free transform an image i had pasted on a new document. now generally when i want to resize it will give me the image shape and when i run the mouse over the corner of the image and hold down shift and alt the image will resize in proportion. however on her computer it would 'distort' rather than resize in proportion. i was wondering how can i reset the 'shift' key on her computer? ive tried doing what the help section suggested with window>workspace>reset keyboard shortcuts that hasnt seemed to work.

does anyone know how to get the 'shift' key working properly again or what the problem might actually be.

many thanks. one thing i know know is why shes had so much trouble re-sizing images within photoshop.