Two things come to mind. First, open a DOS window and run the command kpsewhich ecsi.mf
It should tell you where the ecsi font source code is installed (probably in the jknappen package). If you get a blank line as the response, you need to install a package containing the font. If the font is installed, try opening the MiKTeX settings application and clicking the "update formats" button. I vaguely recall one or two occasions where installation or update of packages through the package manager somehow bollixed the formats, leading to font errors (on installed fonts); updating formats seemed to fix it. Paul
