One of my PCs has developed a new problem with the November update. When I open the start menu, Cortana's CPU usage spikes to 50% and higher (total CPU load hits 100%) which causes a noticeable lag when scrolling in the all programs menu. When the start menu is closed the process' usage usually drops and then it suspends, but for some reason this doesn't always happen and it can remain there for several minutes hammering the CPU.

I have Cortana disabled on this particular machine, inc. history. This problem wasn't there before the current update. I'm also not asking for ways to disable SearchUI, I see there are already many threads about that here.

Any ideas about what could be the cause?