Ah, that explains it; there have been a few thread on that in recent days:
"""
IIRC, some people have reported weird issues with this on Windows. I
don't remember the details, but I think that got resolved - check the
group archives and the community wiki (tiddlywiki.org).
"""
http://groups.google.com/group/TiddlyWiki/browse_thread/thread/9f86c20aa4fbfb81/17716049eb3d5a8b?#17716049eb3d5a8b
-- F.