I've been on Yosemite on this machine since it hit released, and on Fusion 7 since it released. Now on 10.10.1 and 7.0.1 respectively.
On one machine http://www.everymac.com/systems/apple/imac/specs/imac-core-i7-3.4-27-inch-aluminum-late-2012-specs.html everything was working fine, when suddenly both Win 7 and Ubuntu 14.04.1 VMs froze with an "internal VMWare issue". I elected to get the dump from one of them, then when it was done, rebooted the Mac.
Now when I try to start any VM on that machine, I get "Could not open /dev/vmmon: No such file or directory." I tried the http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003484 methods in the KB article, un-install, download, install, repair disk permissions, reboot, and no difference. Anyone seen a way to deal with this?