Why did all Project Level codes disappear?

We're using P6 8.2 EPPM.

I opened a schedule and the Project Level code ID's and descriptions were gone.

I checked several other schedules in the EPS, and they were not there either.

I rebooted my computer but it didn't help.

I closed P6, and opened a schedule and the codes were back.

I opened another schedule and the codes were gone.

I opened the one I opened before and the codes were gone again.

Does anyone know what is going on?

Thanks,

Rob