Ah yes, you must have upgraded to Enterprise Edition 1.6.
One of the "undocumented features" of 1.6 is the ability to disable script tasks among other task types.
The settings that control this ability can be found in the activiti-app.properties file:
# Validator config
validator.editor.bpmn.disable.executionlistener=false
validator.editor.bpmn.disable.cameltask=false
validator.editor.bpmn.disable.muletask=false
validator.editor.bpmn.disable.mailtask=false
validator.editor.bpmn.disable.scripttask=false
validator.editor.bpmn.disable.scripttask.groovy=false
validator.editor.bpmn.disable.manualtask=false
validator.editor.bpmn.disable.businessruletask=false
validator.editor.bpmn.disable.servicetask=false
validator.editor.bpmn.disable.intermediatethrowevent=false
validator.editor.bpmn.disable.startevent.timer=false
validator.editor.bpmn.disable.startevent.signal=false
validator.editor.bpmn.disable.startevent.message=false
validator.editor.bpmn.disable.startevent.error=false
validator.editor.bpmn.disable.startevent.timecycle=false
validator.editor.bpmn.disable.loopback=false
validator.editor.bpmn.limit.servicetask.only-class=false
validator.editor.bpmn.limit.multiinstance.loop=false
validator.editor.bpmn.limit.usertask.assignment.only-idm=false
In your configuration you probably have the following set to true (it is set by default in 1.6).
validator.editor.bpmn.disable.scripttask=true
validator.editor.bpmn.disable.scripttask.groovy=true
Set these to false and you will be back up and running.
Also, be aware that whitelisting (beans and classes) are enabled by default so many of your integrations will likey fail.
Greg
