Recently Google has updated Android Studio to version 0.2.5. There are a lot of complaints about problems with old projects. People are complaining that they are unable to deploy APK file to the device or layouts are not opening. I have spotted the same problem but I was able to fix it. Following are simple steps that did the job for me (IMPORTANT: following is related to new build system projects):
1. Close Project under Android Studio (you can also close Android Studio itself – no matter)
2. Remove .idea folder from your project
3. Make sure all settings are correct (settings.gradle has correct SDK path, build.gradle point to correct build tools version (in my case I had to change buildToolsVersion from “18.0.0” to “18.0.1”)
4. Import the project to Android Studio
After successful import project should build and install correctly. Also viewing layouts works like a charm.