Taks needing and admin password, like deleting certain files in the Finder or running an application installer, hang for minutes with a beachball. After a couple of minutes the dialog asking for an admin password appears finally.
Once the window finally appears it also takes a minute to be usable. After I entered the password everything works just fine.
The same also happens when trying to mount a disk image with a password. It takes minutes for the password window to show up.
I can't see anything happen in Activity Monitor. CPU usage is low and RAM is plentiful. Other applications continue to run quickly.
OS X 10.10.2
MacBookPro11,3 2.8 GHz i7 16 GB RAM