Problem with FMC on PMDG738NKG

 Hi

When I am making a flight plan on FMC,I get some of the information in ok,but before I finish with FP the computer locks up,the screen dims way down

you can still see the plan,but it just sets there,and you can not type any thing else in. this has happen several times.

any body have this proiblem

thanks

Vergil Marequardt