We have an existing class that uses the Test.isRunningTest() method.  Today we tried making changes to that class (completely unrelated to the isRunningTestMethod) and weren't able to save it because of a "method doesn't exist or incorrect signature" error on that method.  Did something change with the Winter 12 release where we can no longer use this in code?  If so, is there something replacing this functionality?  If we should still be able to use it, any thoughts on why we are receiving this error now?

Save error: Method does not exist or incorrect signature: Test.isRunningTest()