help with multiple UNDO operations

[Mickey Ferguson]

I'm using emacs 21.3.1 on Windows 2000.  In the past (version 20.x?) if I
entered C-u C-u C-u C-x u (four consecutive control U characters to set the
argument counter to 64, followed by a control x - u, which performs the undo
command), it would undo the last 64 sequences (character entry, cut, paste,
etc.).  Now it appears that the numeric argument part of the undo command no
longer works.  It always operates as if I had just entered a plain old C-x u
with no prefix.  Has something changed?  I looked in my .emacs and its
associated private library load and saw nothing that appeared to me to have
any possibility of affecting operation in this area.  Any suggestions?