After SDK Update I had the same problems with API Level 19 and
in my case restarting eclipse didn’t solve it.
For some reason, in the sdk/system-images/android-19 directory, sub-folders with system images (armeabi-v7a and x86) were placed within "default" directory.
I just moved them into android-19 directory (if eclipse is running at the same time, you will have to restart it).