Couldn't you just disable / enable frontpage extentions?
I believe I've read somewhere that removing all .htacces files and removing all _ file or something might do the trick. This is only a last resort and I'm not completely sure of it.
The frontpage password is just your DA account login password. (Although, it will remain the same when you change your DA password). If you want to manually change it, I believe they use a standard md5 crypted password in public_html/_vti_pvt/service.pwd, so you could generate your own password in php using:
PHP:
<?
echo crypt("newpassword","randomtext");
?>
and put the encoded password into the file.
But the absolute easiest method to fix the problem is as S2S-Robert said, just disable/enable the extensions. The password is the password you use when logging into DA.