Emacs version: Gnu Emacs 21.1.1 (i386-msvc-nt5.0.2195 of 2001-10-22 on buffy Hi, I,ve found that the Show-button of "C Block Comment Prefix" in *Customize Group: C* results in a non-closeable Hide-button. (I represent buttons below with []) Walkthrough to error: M-x customize Programming group: [Go to Group] Languages group: [Go to Group] C group: [Go to Group] Before pressing Show: C Block Comment Prefix: [Show] State: hidden, invoke "Show" in the previous line to show. Specifies the line prefix of continued C-style block comments. More After pressing Show: >>> /*\ --- JOIN NOW! --- \ / ASCII ribbon campaign X against HTML / \ in mail and news