[ESS] how to reset ESS if color scheme changes?

[Thomas Harte]

my problem description is woefully inadequate, so
apologies before i begin ...

when using ESS (5.3.1) with R (2.3.1) on either linux
or windoze, if i make an error in some commands and
have to C-c C-c, the color scheme changes. for
example, strings, usually highlighted in green, become
black and the R terminal commands, usually highlighted
in black, become highlighted in green.

per my opening remarks, i can't replicate the problem;
it usually happens if i am frustrated with the
keyboard subsequent to having made some input error,
followed by pounding C-c C-c several times, although i
have observed it at other times too.

M-x load-file

/usr/share/emacs/21.4/lisp/ess-5.3.1/lisp/ess-site.el

doesn't solve anything (perhaps it shouldn't anyway).
i should confess to my being a viper-mode character in
the event that this evidence might be crucial to the
resolution of the conundrum.

my question: is there some way of restoring the color
scheme in ESS, short of quitting R and restarting from
scratch?

cheers,

thomas.