I have made a couple of posts at http://bugzilla.gnome.org/show_bug.cgi?id=154968 regarding this issue. A Gimp developer as replied with "You should get in contact with the fontconfig developers as that is their code and we can't really do anything about the fontconfig performance in GIMP." So please check it out. Thanks.
I'd vote for this, but voting doesn't seem to be enabled here. This bug is killing GIMP on Windows.
*** This bug has been marked as a duplicate of bug 12438 ***
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