[ESS] Weird behaviour of assignment symbols with Emacs-24.1 (and ESS 12.04-4)

[John Maindonald]

PS: I forgot to mention.  I am using MacOS 10.7.4

I have just now installed Vincent Goulet's latest Emacs-24.1-modified-1.dmg
for MacOS X, dated 11 June 2012.

If I type
a <- 2
into my R session, the assignment symbol promptly changes to blank space.
Once the command has been executed, the symbol reappears.  This behaviour
happens whether the symbol is entered as <-, or by typing an underscore.

If I open a .R script file, the assignment symbols likewise appear as blank space.
If I copy relevant code e.g. into this email message, the assignment symbols
magically reappear.  Thus, the issue seems to be one of displaying the symbol.

Has anyone else experienced this behaviour? I am guessing that something in
my .emacs file may be interacting with some feature of Emacs 24.1 to cause the
problem.  Any suggestions on what I might check for?

John Maindonald             email: john.maindonald at anu.edu.au
phone : +61 2 (6125)3473    fax  : +61 2(6125)5549
Centre for Mathematics & Its Applications, Room 1194,
John Dedman Mathematical Sciences Building (Building 27)
Australian National University, Canberra ACT 0200.
http://www.maths.anu.edu.au/~johnm