Cannot open the "choose a file" window in any ocasion

Hi folks, my problem is:
I cant open the window to choose the files to upload to a website;
I Cant open that same windo to choose the fileto open with a program (ex: im on paint and i cant open the "choose a file" window to open and edit a photo)
and i cant open that same window in any other program :\
that started to happen after a registry defrag/cleaning, any sugestion?

Thanks for the help

i forgot to m
say that every time that this window should all the open windows blink once as they are going to minimize but then they dont and everything stays as it was.