Wrong type argument: listp, w

[kjetei@online.no (Kjetil Eide)]

Recently I have been getting this errror when attempting to open files in emacs
(version 21.3.2):

Wrong type argument: listp, w

This happens when attempting to open "~/foo.txt" with C-x C-f.
Here's the backtrace:

assoc("/home/kjetilei/foo.txt" w)
save-place-find-file-hook()
run-hooks(find-file-hooks)
after-find-file(nil t)
find-file-noselect-1(#<buffer foo.txt> "~/foo.txt" nil nil "~/foo.txt" (67933 7
74))
find-file-noselect("~/foo.txt" nil nil 1)
find-file("~/foo.txt" 1)
call-interactively(find-file)

Does anyone have any idea what could be wrong?