I have the same problem, home page comes up blank. My log/production.log contains just this:
# Logfile created on Sun Mar 19 01:11:25 Mountain Standard Time 2006 by logger.rb/1.5.2.7
Migrating to Beta1Schema (1)
Migrating to Beta2ChangesBulk (2)
C:\instiki-0.11.pl1>ruby instiki
=> Instiki started on http://0.0.0.0:2500
=> Ctrl-C to shutdown; call with --help for options
[2007-07-26 18:06:46] INFO WEBrick 1.3.1
[2007-07-26 18:06:46] INFO ruby 1.8.6 (2007-03-13) [i386-mswin32]
[2007-07-26 18:06:46] INFO WEBrick::HTTPServer#start: pid=1480 port=2500