I've just upgraded to WFC 6.01g (with Word 2003), and when I launch an analysis (Wordfast Setup > Tools > Analyse), Wordfast actually does the analysis but doesn't display the analysis .txt file anymore (instead of this, it just saves it somewhere + the analysed file's font is changed to Courier New.
I've seen this problem at a client a few months ago. I couldn't find a solution (they had several computers, and only one of them was affected). I asked about it on the mailing list, but didn't get any reply:
Reports files are text files. Wordfast happens to open them in Word, so they will get a font when displayed in Word, but in the end, they remain text files and are therefore fontless.