Can you open a new topic stating all the details of the issue, the browser type and version and steps to reproduce? I take it you are using 4.5 on both client and server sides. Make sure you state this in your new topic. I will be closing this thread, so we can start afresh. We will need the answers to these questions:
The NoMachine products and versions in use on client and server.
Operating system and desktop environment in use on client and server.
If server is Linux: are you connecting to a physical or a virtual display?
Can you provide specific instructions to reproduce the issue?