Planned Value not matching detached BL Cumulative Planned Costs

The Planned Value Cost with the Baseline attached does not match the detached Baseline's Cumulative Planned Cost to the same date.

For example, the schedule with the Baseline attached has a Data Date of October 31st. When we detach and open the Baseline, on the Resource Assignments page, the Cumulative Planned Cost at the end of October is a different number.

Any suggestions?

Thanks,

Jon