vc-git-state(abbrev_defs) -> "Stack overflow in regexp matcher"

[Tom Roche]

I'm running "GNU Emacs 24.0.94.1 (x86_64-pc-linux-gnu, GTK+ Version
2.20.1) of 2012-03-26 on cw-bkp0, modified by Debian" on Linux Mint
Debian Edition, `uname -rv` == 

3.0.0-1-amd64 #1 SMP Sun Jul 24 02:24:44 UTC 2011

I have been

* for several months, versioning my ~/.emacs.d/ using git

* for several years, keeping my ~/.emacs.d/abbrev_defs open in a buffer
  (for ease of adding entries)

* forever, using desktop to maintain buffers between sessions

Just now the box locked up after changing video after a presentation. I 
restarted the OS, then emacs, which produced
 
*Backtrace*
> Debugger entered--Lisp error: (error "Stack overflow in regexp matcher")
>   string-match(...)
>   vc-git-state("/home/me/.emacs.d/abbrev_defs")
>   apply(vc-git-state "/home/me/.emacs.d/abbrev_defs")
>   vc-call-backend(Git state "/home/me/.emacs.d/abbrev_defs")
>   vc-default-state-heuristic(Git "/home/me/.emacs.d/abbrev_defs")
>   apply(vc-default-state-heuristic Git "/home/me/.emacs.d/abbrev_defs")
>   vc-call-backend(Git state-heuristic "/home/me/.emacs.d/abbrev_defs")
>   vc-state-refresh("/home/me/.emacs.d/abbrev_defs" Git)
>   vc-state("/home/me/.emacs.d/abbrev_defs" Git)
>   vc-default-mode-line-string(Git "/home/me/.emacs.d/abbrev_defs")
>   vc-git-mode-line-string("/home/me/.emacs.d/abbrev_defs")
>   apply(vc-git-mode-line-string "/home/me/.emacs.d/abbrev_defs")
>   vc-call-backend(Git mode-line-string "/home/me/.emacs.d/abbrev_defs")
>   vc-mode-line("/home/me/.emacs.d/abbrev_defs" Git)
>   ad-Orig-vc-find-file-hook()
>   vc-find-file-hook()
>   run-hooks(find-file-hook)
>   after-find-file(nil t)
>   find-file-noselect-1(#<buffer abbrev_defs> "~/.emacs.d/abbrev_defs" nil nil 
> "~/.emacs.d/abbrev_defs" (8391858 2053))
>   find-file-noselect("~/.emacs.d/abbrev_defs" nil nil t)
>   find-file("~/.emacs.d/abbrev_defs" t)
>   call-interactively(find-file nil nil)

I

- removed abbrev_defs from my desktop file
- killed the emacs process
- started emacs normally

However I get the error above if I try to open abbrev_defs in a buffer
(`C-x C-f`). How to fix, or further debug?

TIA, Tom Roche <Tom_Roche@pobox.com>