Hi,

I saw the following error message when selecting an nnimap group.

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  gnus-sorted-difference((1928 1929 1930 ...))
  gnus-select-newsgroup("admin.moderator" t nil)
  gnus-summary-read-group-1("admin.moderator" t nil nil nil nil)
  gnus-summary-read-group("admin.moderator" t nil nil nil nil nil)
  gnus-group-read-group(nil)
  call-interactively(gnus-group-read-group nil nil)
  command-execute(gnus-group-read-group)

I think this problem is caused by broken cached headers, because the
attached ad-hoc patch to remove broken cached headers resolves this
problem.  Therefore, if I can remove broken cached headers, the attached
patch is unnecessary.

The problem is that I cannot find the location where the cache is saved.
I have already searched ~/.emacs.d/, ~/.newsrc.eld and the directory
specified by `gnus-cache-directory'.  However, I cannot find it.

Could you give an advise to me?

-- 
TSUCHIYA Masatoshi