I’m facing a strange and productivity destroying problem since this morning.
Properties with no pre filled attributed can’t be edited trough the properties editor. (Margins for example) I need to switch between the view and XML editor every time to made even the smallest change in the world, cause I can only change it from the XML.
I tried everything (Restarting eclipse, every click combos in fields etc…). Really annoying.
The properties editor:

UPDATE: Sound like a problem related to Mountain Lion, so we have to wait for an ADT plugin update ?
This is a limitation in the new property sheet introduced in ADT 20.
We’ve improved it in ADT 21, and if you download Preview 4 (released yesterday) you can see the new behavior. Here’s the fix: https://android-review.googlesource.com/#/c/42238/
Here’s ADT 21 preview: http://tools.android.com/download/adt-21-preview
— Tor