There is a bug in the current version of Kronos that will not let you move time from one code to another using the Move dialog. Follow these steps for a workaround until it is patched in the next release:
Right-click on the time amount you want to move on an employee's timecard and choose "Move".
In the window that pops up, click the box beside Transfer:
The Transfer box should now be empty. Set the Pay Code, Amount and Effective Date, choose OK, and you should now be able to save the employee's timecard.