After upgrading from 1.391 to 1.392, Maven 2.2.1 builds fail when requiring that new artifacts be downloaded from a local Maven repository proxy (Nexus). Even though Maven is configured to use the proxy as a mirror for all repositories, artifacts are attempted to be downloaded from the actual repositories. Downgrading to 1.391 fixes the issue.
<mirrors/>
<mirror>
<id>nexus</id>
<mirrorOf>*</mirrorOf>
<url>http: </mirror>
<mirrors>
<profiles>
<profile>
<repositories>
<repository>
<id>other-repo</id>
<url>http: <releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>other-repo</id>
<url>http: <releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</profile>
</profiles>
Logs report a 407 response when trying to retrieve the artifact from http://www.external.url.com/m2/org/new/artifact/1.1.0-SNAPSHOT/artifact-1.1.0-SNAPSHOT.jar.