Do NOT use regular FTP (such as WS_FTP) to upload files to the server when FrontPage extensions are installed. This may corrupt the extensions, requiring that the extensions be removed and reinstalled.
The one exception to this is when uploading custom scripts to the cgi-bin directory on your site. Using WS_FTP, go DIRECTLY to the cgi-bin directory, transfer the file in ASCII, then right click on the ftp window, select FTP commands, SITE. Then enter CHMOD 755 file. This will properly upload and set permissions for the script.