Could not find any version that matches com.android.tools.build:gradle:0.12.+

I installed Android Studio, installed the JDK, set the environment variables (JAVA_HOME, JDK_HOME, PATH). I configured my proxy (I did the test and the connection works), and when trying to create a "Blank Activity" I get the following error:

Error: Could not find any version that matches com.android.tools.build:gradle:0.12.+. Required by:     : MTest: unspecified

project build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.12.+'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

application build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 'android-L'
    buildToolsVersion "20.0.0"

    defaultConfig {
        applicationId "com.br.mteste"
        minSdkVersion 11
        targetSdkVersion 'L'
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

 dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:19.+'
}

gradle-wrapper.properties

#Wed Apr 10 15:27:10 PDT 2013
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=http\://services.gradle.org/distributions/gradle-1.12-all.zip

I did not make any changes to the gradles (that is, of course I tried several changes, but there was no success in correcting the error so it was back to the default). Does anybody know how to solve this? I searched all day yesterday and found nothing that would solve this ...: /

Thanks in advance.