They can be very complicated to troubleshoot. Unfortunately, I was unable to find anyone that had written a troubleshooting guide for them. I haven't done troubleshooting for them in a few years, because they have gotten much better.
First, make sure that you have all the latest patches. If the problem continues, uninstall the existing FrontPage extensions using add/remove Windows components and then reinstall them. If that doesn't fix your problem, I would backup your IIS configuration and reinstall all of IIS.
Sorry I don't have a more elegant answer -- it is possible to troubleshoot the extensions without removing them, but digging through the FrontPage configuration settings would be impossible for me to document well. Hope it helps anyway.
This was first published in September 2003