I am an experienced graphic designer and I can tell you that once you blur an image it's very difficult to unblur it. The process of blurring an image is destructive, it's like burning a photograph to hide someone's face, after you burn it, it's difficult if not impossible to recover it.
Some types of blurring are similar to a two-way reversible function. By matching the function you can apply the reverse function 'restore' information. deconvolution is a often based on reverse fourier, or wavelet for the theorists.
You could try:
http://refocus.sourceforge.net/
http://refocus-it.sourceforge.net/