Research leads me to believe that there might be a version conflict in the org.apache.http package requested by the aether http transport. The OSGi headers indicate that aether does not express any version contraints for org.apache.http* and therefore might pick up the wrong version (it gets it from org.apache.httpcomponents.httpclient_4.1.3).
Bundle headers:
Archiver-Version = Plexus Archiver
Bnd-LastModified = 1375040107302
Build-Jdk = 1.7.0_25
Built-By = Benjamin
Bundle-Description = A transport implementation for repositories using http:// and https:// URLs.
Bundle-ManifestVersion = 2
Bundle-Name = Aether Transport HTTP (Incubation)
Bundle-SymbolicName = org.eclipse.aether.transport.http
Bundle-Vendor = The Eclipse Foundation
Bundle-Version = 0.9.0.M3
Created-By = Apache Maven Bundle Plugin
Export-Package = org.eclipse.aether.transport.http;uses:="javax.inject,org.codehaus.plexus.component.annotations,org.eclipse.aether,org.eclipse.aether.repository,org.eclipse.aether.spi.connector.transport,org.eclipse.aether.spi.locator,org.eclipse.aether.spi.log,org.eclipse.aether.transfer";version="0.9.0.M3"
Import-Package = javax.inject;resolution:=optional,
javax.net,javax.net.ssl,org.apache.http,org.apache.http.auth,org.apache.http.auth.params,org.apache.http.client,org.apache.http.client.methods,org.apache.http.client.utils,org.apache.http.conn,org.apache.http.conn.params,org.apache.http.conn.scheme,org.apache.http.conn.ssl,org.apache.http.entity,org.apache.http.impl.auth,org.apache.http.impl.client,org.apache.http.impl.conn,org.apache.http.impl.cookie,org.apache.http.params,org.apache.http.protocol,org.apache.http.util,org.codehaus.plexus.component.annotations;resolution:=optional,org.eclipse.aether;version="[0.9,1)",org.eclipse.aether.repository;version="[0.9,1)",org.eclipse.aether.spi.connector.transport;version="[0.9,1)",org.eclipse.aether.spi.locator;version="[0.9,1)",org.eclipse.aether.spi.log;version="[0.9,1)",org.eclipse.aether.transfer;version="[0.9,1)",org.eclipse.aether.util;version="[0.9,1)"
Manifest-Version = 1.0
Tool = Bnd-2.1.0.20130426-122213
I tried with eclipse 3.6.2 and eclipse 4.3.1 (3.6.2 needs Orbit to successfully install aether)
Any help is highly appreciated.