Hi i tried to migrate my ovirt engine form a centos 8 to a 9 machine. So, I made a backup, created and configured a new machine, stopped the old one, started the new one with identical network configuration, restored the backup and tried engine-setup to set up the new site, exping it to work. It did not, but I thought, no prob, I still have my old one. Now, going back to the old mache, when logging into Admin Portal, I get error messages: - Error while executing action: A Request to the Server failed: Type 'org.ovirt.engine.core.common.queries.QueryType' was not assignable to 'com.google.gwt.user.client.rpc.IsSerializable' and did not have a custom field serializer. For security purposes, this type will not be deserialized. - Error while executing query: null Each in a Box, which I clicked away getting the messages toggeling. After a while, the abckground of the admin Portal's dashboad is becomes visible, but remains empty, with the 'loading' spinner. In the serverlog I only see the following exveption: Caused by: com.google.gwt.user.client.rpc.SerializationException: Type 'org.ovirt.engine.core.common.queries.QueryType' was not assignable to 'com.google.gwt.user.client.rpc.IsSerializable' and did not have a custom field serializer. For security purposes, this type will not be deserialized. at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.LegacySerializationPolicy.validateDeserialize(LegacySerializationPolicy.java:128) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserialize(ServerSerializationStreamReader.java:676) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.readObject(ServerSerializationStreamReader.java:592) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.core.java.util.Collection_ServerCustomFieldSerializerBase.deserialize(Collection_ServerCustomFieldSerializerBase.java:38) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.core.java.util.ArrayList_ServerCustomFieldSerializer.deserialize(ArrayList_ServerCustomFieldSerializer.java:40) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.core.java.util.ArrayList_ServerCustomFieldSerializer.deserializeInstance(ArrayList_ServerCustomFieldSerializer.java:54) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.core.java.util.ArrayList_ServerCustomFieldSerializer.deserializeInstance(ArrayList_ServerCustomFieldSerializer.java:33) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserializeImpl(ServerSerializationStreamReader.java:887) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserialize(ServerSerializationStreamReader.java:687) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.readObject(ServerSerializationStreamReader.java:592) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader$ValueReader$8.readValue(ServerSerializationStreamReader.java:149) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserializeValue(ServerSerializationStreamReader.java:434) at deployment.engine.ear.webadmin.war//com.google.gwt.user.server.rpc.RPC.decodeRequest(RPC.java:312) ... 64 more Which , of course I do not understand, what it tries to tell me. The VM-Portal is still reachable, and seems to work. Has anybody had an effect like that, or, even better, an idea, what I am doing wrong and how I can fix that, or where I can look to find the main cause for the bahaviour- Forgot to mention: Desperate, as I am, I also tried to upgrade to 4.5.7-master, which worked without any problem or warning, but the effect is still the same. Thanks and best regards Steffen