org.codehause.groovy.eclipse.codeassist.completion plugin throwing runtime exception.

When using the key shortcut for code completion in GGTS a pop up appears stating that a runtime exception has occurred in the org.codehause.groovy.eclipse.codeassist.completion plugin because it did not complete normally.

I then click OK to close the pop up. When I try to save my work, clicking the save button does nothing. I have to close GGTS and restart losing all of my unsaved work.