This sounds like it works as it should. Once you fail a test step, test case fails. And once the test case is flagged as failed, SoapUI does not reset it to passed in the same run.
The fact that you are rerunning the step doesn't matter. Think about Data driven testing; there by design you are running the same step many different times looking for a failure, and once you encounter it you fail the test case.
nmrao had the right suggestion to use a script assertion that doesn't fail the first step if the login wasn't accepted.
Michael Giller
SmartBear Software
