Cannot create any projects via mvn archetype:generate

Hi,

I am pointing to http://repository.sonatype.org public group in my maven settings.
Last time I tried to create a project via mvn archetype:generate i got an error saying that
org.apache.maven.plugins:maven-archetype-plugin:pom:12-SNAPSHOT is missing.

I did some digging and found out that it comes from http://repository.sonatype.org
mainly from here:

http://repository.sonatype.org/content/groups/public/org/apache/maven/plugins/maven-archetype-plugin/

maven-metadata.xml lists up to 12-SNAPSHOT, but there are no such artifacts there.

Could somebody do something about it or how do I fix that on my side?

Thank you.
Alex