<http://buildbot.mongodb.org/builders/Windows%2064-bit/builds/474/steps/test_1/logs/stdio>

From the log it looks like the shell might not have waited for mongod to have completely finished before continuing with the test. It's possible that wait_for_pid returned prematurely, and looking at the doc for GetExitCodeProcess it seems that this function may return true even if the process is still running.
<http://msdn.microsoft.com/en-us/library/ms683189(VS.85).aspx>