Dear Torsten,
you tried it with sbcl and cmucl and get basically the same error?
For the sbcl case - maybe it would be good just to try with 0.9.16 ? Just to be sure: You are invoking it with $ ./install.sh --sbcl (no other options?)
A friend of mine had a problem _using_ the fomus cmdline app... The error message was similar (if I remember correctly).
It showed up, that the encoding of his text input file was unicode.... Changing it to Latin-1 made it work!
There is even a 0.9.16 binary release available on http://sbcl.sourceforge.net/platform-table.html, so again, its probably best to try that.
Have you successfully compiled and used fomus from the Lisp REPL?
Hope that helps somehow, if not, I am sure that David will now, but he might need a longer backtrace then... ;-)
Cheers,
Kilian