Yes and no. It is not unethical or unfair to kick you out of the CVICU, even after only a month, even without screw-ups, if, in their subjective judgement, they deem you unprepared for the position. It is all about patient safety, as mentioned before. But it is highly unethical, in my opinion, to leave you hanging high and dry without another staff RN opportunity in the hospital, if, as you mentioned in your post, there were never any gross negative issues with your performance in the ICU (such as lying, stealing, abusing patients etc). If that is how the hospital treats its nurses, I would be glad to have gotten out of it, this is not really a place where you want to work.