Vim and folding

["Sridhar M.A." <mas@uomphysics.net>]

At the end of my tex files, I have the following line:
  
    % vim:fdm=marker:tw=72:et:sw=2:ts=2:

With that, I had enclosed ranges of lines between the fold markers {{{
and }}}. Whenever I opened such a file in vim, those lines appeared
neatly folded. Since morning, I am noticing that folds are no longer
honoured. Moving over to a line with {{{ marker and issuing a zc does
nothing except informing me "No folds found"! After some experiments, I
could get back the behaviour by doing an explict set fdm=marker (either
inside a session or ~/.vimrc). Obviously, settings given at the end of
file are not being read and/or honoured.

My question is, why this sudden change in the behaviour of vim settings
given at the end of a file? Can I get back the earlier behaviour?

Regards,

-- 
Sridhar M.A.

<jgoerzen> doogie: you sound highly unstable :-)
<Knghtbrd> jgoerzen - he is.
* doogie bops Knghtbrd
<Knghtbrd> see?  Resorting to violence =D