E9 Cycle Count Problem

We are currently running a pilot of E9.04.506c and we are having a problem with the new cycle count function. We have created three count periods and began counting in period #1. We tried to run the function "Perform Part Selection" in the Cycle Count Schedule Maintenance screen and it locks up every time. What are we doing wrong? Do you have to complete/close the prior period before you select anything in the next? If anyone has any advice on running the new cycle count functions it would be greatly appreciated. Thx!