Win + X Shortcut not working

I am having this peculiar problem for several months. The W+x shortcuts are not working which is very irritating.

I use my keyboard the most, even for navigation. It is very frustrating to use more key strokes to open new windows or to show desktop. I use mouse only when I have to design some thing like creating a drawing object in word, resizing tables, during photoshop sessions etc.

But mostly my work revolves around the keyboard and I use these shortcuts very much. This problem is bothering me too much.

Am using Win xp sp2 pro