I have faced following weird exception on GGTS IDE .
Command terminated with an exception: org.grails.ide.eclipse.longrunning.client.GrailsProcessDiedExc
This link suggests a workaround for your error message.
I remember that I encountered this problem firstly with GGTS 3.2.0 and solved it with the following workaround: In GGTS click
Preferences -> Groovy -> Grails -> Launch Grails and uncheck “Keep external Grails running“.
The workaround was suggested by https://issuetracker.springsource.com/browse/STS-3277 and the issue is marked as solved, but obviously it still exists at least in GGTS 3.4.0 and GGTS 3.5.0.M1.
Nevertheless, while using the suggested workaround (uncheck ”Keep external Grails running“) the GrailsProcessDiedException disappeared and the problem was solved.
Regards