v4.5.1 is also broken for me too (full log below). Downgrading to v4.0.1 was the only way for me to keep working with our REST services over HTTPS.
Thu Sep 13 14:04:56 PDT 2012:ERROR:java.lang.ClassCastException: org.apache.http.message.BasicHttpRequest cannot be cast to org.apache.http.impl.client.RequestWrapper
java.lang.ClassCastException: org.apache.http.message.BasicHttpRequest cannot be cast to org.apache.http.impl.client.RequestWrapper
at com.eviware.soapui.impl.wsdl.support.http.HeadderRequestInterceptor.process(HeadderRequestInterceptor.java:42)
at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:108)
at org.apache.http.protocol.HttpRequestExecutor.preProcess(HttpRequestExecutor.java:174)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport$SoapUIHttpRequestExecutor.preProcess(HttpClientSupport.java:106)
at org.apache.http.impl.client.DefaultRequestDirector.createTunnelToTarget(DefaultRequestDirector.java:830)
at org.apache.http.impl.client.DefaultRequestDirector.establishRoute(DefaultRequestDirector.java:739)
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:565)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:415)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport$Helper.execute(HttpClientSupport.java:236)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport.execute(HttpClientSupport.java:345)
at com.eviware.soapui.impl.wsdl.submit.transports.http.HttpClientRequestTransport.sendRequest(HttpClientRequestTransport.java:241)
at com.eviware.soapui.impl.wsdl.WsdlSubmit.run(WsdlSubmit.java:123)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
