well, its a clear abendging issue. the msg say your MAT transaction is abended.
Do the follwing step to know you abend code
logout of all the screens, infact logout of the session,
type AADF ( Its Abend Aid Diaognastic Facility )
it shows all the abends for the regions with transaction name and prog name.
take you cursor to list the select the one which you are getting. The list will be having the date and time of abend.
This AADF has lot of help options where you can check file defination, its length when the prog is compiled, and .......
try out. Hope this wud help you.