I am testing Ubuntu 17.10 Desktop as a Virtualbox 5.2 guest. The Virtualbox guest additions are installed from Virtualbox Addition ISO. Virtualbox itself is running on a Ubuntu 16.04 host.
After a first view everything works fine. But as soon as I start the Firefox browser any application windows are frozen for several seconds. There are no special activities in the system visible, nor is there any warning or error in syslog.
The "frozen" situation stays also, when I kill the firefox process. After system reboot everything works fine as long as I start Firefox again.
Working with Chromium does not cause any problems.
Any ideas what I can do to solve that problem or what I can check?