Review the Change Auditor Client log (may need to run the client as Administrator and enable debug logging) looking for an error similar to the following:
[ERROR][ChangeAuditor.MainForm.Application_ThreadException(0)] Error creating window handle.
If that error is shown, the ChangeAuditor Client Profile may be corrupt and may need to be re-created (ApplicationState.xml)
Sometimes, the ChangeAuditor Client may behave strange with search permissions and / or profile authentication.