How did you install Eclipse? If you installed Eclipse from the Ubuntu Repos... I advise against this. It is better to download and install Eclipse from an official Eclipse download site. E.g. from eclipse.org.
Or even easier is to download and install a bundled GGTS which alreayd has Groovy and Grails tools installed.
I'm not exactly sure what is going wrong with your installation. But we have had reports in the past of problems with people using Eclipse's from the Ubuntu repos. These repackaged versions may seem to work fine at first but they are sometimes incomplete. They are also setup to be shared among multiple users. But this means that the 'central place' where you typically install other plugins and extensions is not write-accessible. This creates problems for certain kinds of extensions known as 'feature patches' (and GGTS has some).
It is still very strange that your installation seems to have worked without any errors, yet the plugins are not enabled when you run.
I will try to reproduce your problems shortly, but in the mean time if you installed from Ubuntu Repo, could you please try again with an 'official' distribution of Eclipse instead. Install this in your user home directory. Don't try to make it a 'shared' setup.
Last edited by Kris De Volder; Sep 4th, 2012 at 11:23 AM.
Kris De Volder -- SpringSource