Probably the error occured by opening version 9 in a free version. The large number of nodes in the file can't be handled then. Activated the version 9 with the license key. Problem solved
I have renamed the mecway.exe in wecway8.exe and mecway9.exe and assigned the .liml extention to mecway9.exe.
Can now open the files in version 9 and by double klicking on the file extention.
I can continue working :-)