How this usually happens is that there's a notification indication. I'd click on the clock to show the notification center, dismiss the notification, and the clock would slide "too much" to the right, so that almost half of it is outside the screen.
A quick google search doesn't bring my issue up (I'll try to take a screenshot next time it happens, but I'm usually too annoyed of having to use windows to think about it). But it did bring up a separate issue, where the right-hand side icons area (system tray?) and the clock are moved down so that only the top of the date is showing. I've never had that one.
I think these are lag-related, as in things move when something opens. But if the thing before didn't complete or something, the new thing happening doesn't get to remove the old one as expected.
The other day, on a PC that was doing whatever it is that windows does when the CPU fan goes full tilt while pretending to be asleep (complete with the blinking power light), after waking it up, I managed to have both the notification center and the quick settings displayed. I mistakenly clicked on the notification, then immediately on the settings. The notification panel took forever to show up, and it showed while the settings panel was still showing.
