Also note that Repository should provide an index in first place for this option to work.
I believe there is solution in following link: stackoverflow.com/questions/7065478/classic-error-unable-to-update-index-for-centralhttp-repo1-maven-org-maven2 : stackoverflow.com/questions/7065478/…
You can also get this if you are using Maven proxy (Nexus, for example) and the index into the proxy is messed up somehow. Fool around with it or call the one who set up the Maven proxy.
You can also get this if the new workspace hasn't yet downloaded the index either from Maven central or from the proxy.
eclipse artifacts search depends on repository's index file, it seems, you did not download index file.