Jared--encountered the same issue.
If you modify line 463 of
C:\RailsInstaller\Ruby1.9.3\lib\ruby\gems\1.9.1\gems\ocra-1.3.1\bin\ocra
(or wherever that file is located for your version of ocra)
to instead read:
modules_to_check << mod unless modules_checked.include?(mod) if !
mod.name == 'ThreadSafe::JRubyCacheBackend'
It should work for you! Hope this helps!
Best,
Drew