Vladimir, There is a conflict between parenscript and css-lite. Css-lite redefines the parenscript operator % (javascript modulo operator) css-lite.lisp: #+parenscript (ps:defpsmacro % (val) `(ps:+ ,val "%")) causes this behavior: ; SLIME 2008-07-05 CL-USER> (lisp-implementation-type) "SBCL" CL-USER> (lisp-implementation-version) "1.0.18" CL-USER> (require :parenscript) NIL CL-USER> (in-package :parenscript) #<PACKAGE "PARENSCRIPT"> PS> (ps (% 3 2)) "3 % 2;" PS> (require :css-lite) NIL PS> (ps (% 3 2)) error while parsing arguments to DESTRUCTURING-BIND: invalid number of elements in (3 2) to satisfy lambda list (CSS-LITE::VAL): exactly 1 expected, but 2 found [Condition of type SB-KERNEL::ARG-COUNT-ERROR] andy