GroovyCategorySupport has bug in methods prioritization logic, that can lead to infinite loop.
Please try this snippet in groovy 1.6-beta-2:
groovy -e "org.codehaus.groovy.runtime.GroovyCategorySupport.use(groovy.servlet.ServletCategory,
I just tried it in specified version of Groovy, downloaded from http://build.canoo.com/groovy/artifacts/20080603122913/dist/groovy-binary-1.6-beta-2-SNAPSHOT.zip
Groovy hangs up.
The solution is quite simple (see patch).