Tried to update through the app store. The update seem to work fine, but at the end I got an error, stating that the update was damaged and that I had to try again. But the update doesn't appear in the app store again.
So I downloaded the update combo, to update my iMac manually. Tried to open the image file, but got an error saying the image file was damaged and couldn't be opened.
I've pretty much had it for today.