The rcirc logging facility doesn't play nicely when it comes to
writing process buffers (or "server buffers") to disk on Windows
systems. The generated log filenames contain asterisks which are not
allowed on Windows systems. This makes rcirc and Emacs as a whole
unusable when rcirc-log-flag is non-nil, i.e. when logging to disk is
turned on. Emacs just messages errors in the echo area when this
happens and you can't easily stop it.

Attached is a patch which introduces a new function and a new
customizable variable.

rcirc-generate-log-filename is the function which takes care of
generating filenames for rcirc buffer logs. It is now the default
instead of the old rcirc-generate-new-buffer-name.

rcirc-log-process-buffers is the new variable which decides whether or
not to log process buffers to disk at all. I get the feeling that not
that many people are interested in logging this as it rarely contains
any useful information that you would want to store. Nevertheless, the
variable is non-nil by default which turns on process buffer logging.

The setup I'm using by the way:

In GNU Emacs 24.0.50.1 (i386-mingw-nt6.1.7600)
 of 2010-08-02 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 6.1.7600
configured using `configure --with-gcc (4.4) --no-opt --cflags -Ic:/xpm/include'

-- 
Deniz Dogan