I'm running Ubuntu 13.04 64-bit as a guest, on Windows 8 Pro host. My CPU is an Intel 3970x. Fresh install from the ISO, installed Guest Additions the first thing after OS.
3D acceleration works, everything seems to work fine (except System Settings in Ubuntu segfaults, but that's not the issue here). However, whenever I go into fullscreen mode, the Virtual Box mini toolbar (the one that's supposed to be a 1px line that pops up when you hover over it) is nowhere to be found. It shows up during the boot procedure, but that's it. The Host+Home menu doesn't show up either. This makes it practically impossible to tell virtualbox to run the VM on a specific monitor.
Has anybody encountered this before? Is there a known fix?