Hi,

I'm getting the same problem in Emacs 22.2.1 in Ubuntu. Steps to reproduce.

1. start emacs without any resource file (.emacs or any other rc file)  <---
this is avoid if there is some problem with user init file.
2. open file called 'test.c'
3. copy content of "http://www.rfc-editor.org/rfc/rfc2547.txt" into test.c
and save it.
4. do  C-k till section "3.1 Virtual Sites" in the current buffer.
5. Trying continuous C-/, emacs is **not** getting into beginning of the
buffer. I get only few lines as undo. Just 5 lines i can do undo. Not more
than that.

Without font-lock-mode (after disabling font-lock-mode), i tried same
sequence, i can get some more lines in undo but not the whole buffer. So, as
you pointed out font-lock-mode has some impact with undo.

Increased undo-limit,undo-strong-limit,undo-outer-limit to 100,000,000. I
repeated the same steps from 1, 5. This time, I'm able to do full undo.. I
dont mind setting this value in my .emacs because memory is not a problem
for me. But, would this cause any other problem like performance or buffer
loss ?.

Thanks,
Regards,
Suresh Kannan.