In the eclipse installation directory /usr/local/lib/eclipse there are some
files that are not readable by non root users, expecially in plugins
directory (java.*.jar and others). In errors view pane there are errors
related to java when it try to open that plugins. This, in some way,
prevents installing new plugins from eclipse internal update manager.
I don’t remember what files are rw-------, however I scanned all
/usr/local/lib/eclipse files and subdir and set read flags for all