In the past month there have been 3 reports from users that Windows Live Writer will not start up. After looking in the Windows Live Writer log file, the following exception was seen:
An unexpected error has occurred within the application.
System.ArgumentException: Font 'Courier New' does not support style 'Regular'.
These reports have come on both Windows Vista and Windows 7. Even after checking that the Courier New font file was still there, still signed by Microsoft, and the file size was the same as another computer… there was something wrong with the font. Even double clicking it produced a window which shows the font correctly:
Replacing the font files from another computer has fixed the problem all 3 times. Simply copy the C:\Windows\Fonts\cour.ttf from another computer to the broken machine.
Email me at bturner [at] microsoft [dot] com if you are still having problems even after replacing the file.