You run Groovy -Eclipse for Eclipse 3.5 in Eclipse 3.6, so it is broken. I am surprised that you can even install it. You need to install the Groovy -Eclipse snapshot version for version 3.6. Only zip file available:
http://dist.codehaus.org/groovy/distributions/greclipse/snapshot/e3.6/
Download the archive and point your p2 installer to zip. You can install stream 3.6 from Groovy -Eclipse. Formatting follows.
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