I am running Fusion 7 on a MacBook Pro Retina 15" early 2013 with Mac OS 10.10 Yosemite Developer Preview 8. I am running a Windows 7 Pro 64-bit VM with latest VM Tools installed, running in full-screen mode on a second monitor.
From time to time, the VM's screen will freeze. From what I can tell, the VM is still running, but the display stops updating. Everything looks fine, but nothing appears to happen when you click in the VM window. It is easily fixed by minimizing and then un-minimizing the VM window, or by suspending and then resuming the VM.
When the VM comes back up, it becomes apparent that your clicks actually did go through (i.e. windows you tried to close are now closed, icons you thought you had clicked on are selected, etc.), so it seems like a problem with the display driver. Whether it is the VM display driver or the Mac display driver is anyone's guess.
I'm seeing the same thing on the same MacBook Pro connected to a Thunderbolt monitor. It happens within a few minutes if I scroll a page in Safari. Screen updates are pretty slow, even before they stop.
I haven't reported it to support only because Yosemite isn't officially released yet.
I haven't seen the problem lately, so it may have been fixed in one of the Yosemite developer updates. Granted I might not have triggered the source of the problem since the last occurrence.