Remote server - menus disappear

[clm]

On our remote access server, all users even when logged on server locally are currenlty experencing issues when they click and hover on start menu and try an launch a program or when they are in a program ie word they try and change font in the drop down menu and menu selection disappears after 3 seconds or so before you can make a choice. This is very annoying and has only been reported to us about a week ago.

anybody else come accross this or know what it is called so we can have a go at fixing, we have checked log files and nothing is showing as warnings or errors