2nd Monitor causes Cubase Project menus to freeze

The description above says it all.
I have to unplug my 2nd video monitor (used for my mixer) in order to open drop-down menus in the project screen or save a project.
Running on Dell XPS Laptop

Can anyone suggest why this behaviour happens please?
thanks, joe

Do you use integrated video to run your monitors? If so, maybe you need a dedicated graphics card.

Thanks Poinzy but I’m using a laptop.
My tower PC doesn’t show this error,
joe