can't generate 2-port ROM with megawizard

Hello

i want to generate a 2-port ROM using megawizard.

so i click "tools" and go into the megawizard plug-in manager [page 2a].

i select the "ROM:2-PORT" below the "memory compiler".

then i click next it goes to the ROM:2-PORT [page 3 of 8]--the "parameter settings" window

but when i click next it returns to [page 2a] or sometimes the window just disappear.

i have tried others like ROM:1-PORT RAM:3-PORT RAM:1-PORT

they all work right.

why ROM:2-PORT can't

thank you

btw, my quartus ii version is 9.1