I managed to set up spork on Windows 7. The spork server is running in a command window. I'm using Rubymine 3.1 and Ruby 1.9.2.
Running autotest, rspec spec/ and rake spec from the command line runs fine and performs all tests correctly. Running rake spec from within the RubyMine environment always results in:
C:\Ruby192\bin\ruby.exe C:\Ruby192\bin\rake spec
Testing started at 6:51 PM ...
Empty test suite.
Process finished with exit code 0
"No tests were found"