Any of the following can cause Frontpage Extensions to corrupt:
1. Using FTP to upload or edit site files. It is strongly encouraged that you do not use FTP to upload or modify any of your site files other than to upload to your public_ftp or cgi-bin folders. WS_FTP is particularly dangerous to use as it leaves a small log file "WS_FTP.LOG" in each directory. This file can cause the FrontPage extensions to corrupt, as they do not know what to do with it.
2. Running CGI scripts. FrontPage extensions can become corrupted when running certain CGI scripts and may also damage the script itself.
3. Editing ".htaccess" files. FrontPage uses ".htaccess" files. Editing your .htaccess files may corrupt your FrontPage extensions.
4. Reaching your maximum storage quota. If your account reaches its maximum storage quota, your FrontPage extensions may corrupt. For each child web you publish, FrontPage duplicates certain information into indices and hidden files. This adds "overhead", increasing the storage space required for your files.
5. Too many files in a directory. This is rare, but possible. Attempting to open a directory with too many files can sometimes cause FrontPage Extensions to corrupt. While there is not a set number, this seems to start appearing when there are more than 100 files in the directory.