I recently got a problem to publish from Microsoft Expression Web 4 to my website. Strangely enough the error message shows in German even though the application is English as well as Windows and locale settings.
Microsoft Expression Web: Server error: Web "<Stammweb>" ist ausgelastet. Versuchen Sie es später wieder.
In the connection settings I use FrontPage Server Extensions and I have not changed anything after the point it worked and when it stopped working.
My website host company could not find anything wrong either but after they restarted the server it worked again for me.