I had a similar problem when I started my PC tonight. Have you recently installed SP2 ?
Try click here
For me it was a simple fix as I save all my fonts on a CD. Have you an old Windows 98 installation disk ? If so you could try and download the font files to your fonts folder.
Click on 'Control Panel' and switch view to 'Classic', the fonts folder will be shown, open it and click on File and drop down to 'Install new font', search for the fonts on your old installation disk, select 'all' and press OK. Reboot your PC and everything should go back to normal.