Steps to reproduce the issue:
1 - Get a clean eclipse install by APT (apt-get install eclipse)
2 - Help->Install New Software
3 - Using this update site http://dist.springsource.org/release/GRECLIPSE/e3.7/, install "Groovy-Eclipse (Required)". Restart Eclipse.
4 - In Help -> About Eclipse Platform, the groovy icon does not appear, but can be see in "Installation Details". I don't any plugin stuff like create a groovy project, create groovy class, etc.
If I try to install other plugins, and then install the groovy-eclipse, all other plugins stop to work, including the groovy-eclipse.