When front page extension are installed, the 'ownership' in linux terms is changed to an other user - so that FP extensions work. Therefore, you can no longer FTP into your account - you have to use Front page. (even if the extension got broken, the ownership is still the same so you can't FTP into your domain.)
What you have to do, is contact support. Explain the problem, and they will reinstall FP extension for your domain, and then things will begin working again as they did before. Alternativly, if you are ready to ditch FP extensions, and go the FTP route you'll still have to contact support and ask them to remove the extension from your website.
Apparently the upgrade to Debian sarge has messed up FP extension for a few websites - as this was all posted in the forum before.