This is probably something on the server end, but just to eliminate any other possibilites make sure you're not trying to publish from behind a firewall that's blocking FP.
If you are using the Frontpage publishing routine and don't have server extensions installed, install them from your control panel or ask your host to do it.
If you are using the Frontpage publishing routine and [i]have[i] FP server extensions installed, go to your control panel and see if there's an entry to "Repair" the extensions. Give that a shot. If that doesn't do it, first "uninstall" then reinstall the extensions (or ask your host).
But...it actually sounds like you're trying to FTP the files with Frontpage. That could go back to a firewall problem or a permissions problem or something just hinky on the server. If anything above doesn't clear it up you'll probably have to contact them.
Oops, forgot to add: On an Apache server the server extension repair and install routines overwrite the existing .htaccess file. So, if you are on an Apache server and do use the server extensions and have made modifications to your .htaccess file, be sure to make a backup copy before fiddling with the extensions.