There is a connection leak triggered when using the Browse Remote feature.
Logs contain these types of messages:
2015-02-23 08:57:27 WARN [850148762-12088] - org.sonatype.nexus.plugins.rrb.MavenRepositoryReader - Failed to get directory listing content
org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool
Under normal circumstances the leak is handled gracefully by GC and HttpClient. Still, in case when remote uses Content-Encoding: gzip and/or chunked transfer encoding, the connections are NOT reused even after longer period, leading to connection pool depletion.
When I'm browsing a remote maven repository in 2.11.1-01, after maybe ~20 steps through the remote repository tree, I get an infinitly spinning cirle. Refresh doesn't work either. The only way to continue browsing the repository is to restart Nexus.
This seems to impede all communication with the remote repository. Downloading a file that has not yet been cached locally doesn't work either in this state.
For immediate mitigation a Nexus restart is required to free the leaking connections.
For temporary mitigation until you upgrade to a fixed Nexus version, install the version specific patched jars attached to this issue.