Note Make a backup of the Microsoft Forecaster 7.0 SQL database before you make any of the changes listed here.
There are two ways to workaround this issue.
Option 1:
If you want to prevent the data in these periods/columns from changing, set the periods to Historical instead. You can set them to Historical in the client by clicking Setup, pointing to Segments and then clicking Period. Then clear the locked column for these periods by clicking Setup, pointing to Budgets and then clicking Input Set.
Option 2:
If you want to let HR calculate on these Locked periods, you can change the option by clicking Setup, pointing to Budgets and then clicking Input Set. On the Locked Periods tab, click Custom and then check Allow Details. This will enable all the detail modules (Capital, HR, Revenue) to still calculate on the locked periods and will prevent the crashing.