error in replace-match: "args out of range"

[ken]

replace-match works fine in a couple instances in one function, but this
instance (in the same function) it doesn't.  I get the error msg below
about the arguments being out of range.  I'm guessing the problem is
with the 4th arg, the one beginning: #("<a ... yes?  There's a lot of
"(fontified ..." cruft in it... is that confusing replace-match...?  Or
might I have just the totally wrong type arg there?

Debugger entered--Lisp error: (args-out-of-range -1 -1)
  replace-match("Text for Heading" t nil #("<a
name=\"Testing-TOC-Header\"></a>" 0 1 (fontified t face
font-lock-function-name-face) 1 2 (fontified t face html-tag-face) 2 3
(fontified t) 3 8 (fontified t face font-lock-variable-name-face) 8 9
(fontified t face font-lock-string-face) 9 27 (fontified t face
font-lock-string-face) 27 28 (fontified t face font-lock-string-face) 28
29 (fontified t face font-lock-function-name-face) 29 30 (fontified t
face font-lock-function-name-face) 30 32 (fontified t face
html-tag-face) 32 33 (fontified t face font-lock-function-name-face)) 4)
  eval((replace-match head-text-nested t nil head-text 4))


-- 
Anything is easy if you know how to do it.