uPVC window lock broken?

I have uPVC double glazing and the locks run along the bottom of the window. It appears that the mechanism doesn't work properly. I can push the window open while locked with minimal resistance. The locking parts don't appear to move either corner of the window or at the handle position.

Is this fixable, would it be something an experienced DIYer could do or would I need a professional?

Thanks

Sarah
November 2008