Character rendering doesn't run well

Hi all,

I have Windows Vista SP2 just updated. Some days ago I runned the magnify
program (C:\Windows\System32\Magnify.exe) to check graphics on my projects.
The screen flashed a while, the program started, but Windows stopped to show
in a right way smoothed characters of some texts on the screen. I tried to
reinstall drivers of the graphic card, I tried to use another graphic card,
but it continue to show wrong characters. It seems that Windows don't know
how to generate a correct antialiasing. I see some characters where there are
vertical lines designed with a width less than one pixel (the only one is
lightly gray instead black) and, in a text with the same font, some other
characters have the central pixel black and two pixels on the left and two on
the right smoothed.

I switched off the character smoothing, but I'd like to use that. When the
character smooting is switched off, some texts are still smoothed, and thoose
texts are smoothed well both with the smoothing switched on and off.

What I have to do?