What happens when we press Ctrl+Z,while creating process or wsdl file in Tibco BussinessStudio 6.When I press Ctrl+Z ,my project stopped working.

I was creating a subprocess having Soap WebService,having CRUD operations  and calling it through a process,having rest WebService(as given in BookSamples example).

If by mistake i deleted some activity and press Ctrl+z ,then my project stopped working it throws error.Same case occur while making changes in the wsdl file,it also threw error after I pressed ctrl+z, and project become impaired.

Can someone have an answer?