vc-mode and integerp, nil

[C]

Over the last few months I've begun to see this problem more and
more. I use the xemacs package from the Fedora repositories and
usually update packages every few weeks or so. Currently I'm on F11
with XEmacs 21.5.29 "garbanzo" but this issue has been present for a
few releases now.
When I try to open a file that is under source control SVN or GIT I
get an error "Wrong type argument: integerp, nil". If I take the
(require 'vc)
line out of my "~/.xemacs/init.el" the error never ocurs. The
difficulty with this is that ediff called through svn-status requires
vc-mode and as soon as I load the vc package XEmacs refuses to load
the files I'm trying to diff, essentially rendering XEmacs useless for
day-to-day use.
I'm hoping someone will have seen this or be willing to work through
this. Even a pointer to the problem would be a start. Here's a
backtrace from a find-file:

Debugger entered--Lisp error: (wrong-type-argument integerp nil)
signal(wrong-type-argument (integerp nil))
byte-code("..." [buf data kill-buffer signal] 3)
find-file-noselect("common/main.c" nil nil t)
#<compiled-function (filename &optional codesys wildcards) "...
(77)" [wildcards filename coding-system-for-read codesys bufname value
get-coding-system find-file-noselect nil file-exists-p buffer-file-
name local-variable-p buffer-file-coding-system switch-to-buffer
mapcar] 6 1195164 (list (read-file-name "Find file: ") (and current-
prefix-arg ...) t)>("common/main.c" nil t)
call-interactively(find-file)