CDKScheduler has not been made multi-record aware. If you schedule multiple shows at the same time same tuner with the XRecord schedule button and run CDK from the stop menu does only one get scheduled? They should end up in the pending. If you run priorityrecordings.exe from the command prompt you can see from the output what CDKScheduler is doing and why. I'm pretty sure the concurrent recordings will be seen as conflicts.
You could try this in priorityrecordings.xml's Configuration section to ignore conflicts.
Maybe some other CDKScheduler users who unlike me have gone digital can give some advice...
2 Hauppauge PVR-150's, Celeron 2.93GHz, 1GB RAM, 1TB Maxtor HD, Cooler Master Cavalier 2, Radeon HD 2400 Pro, gbpvr 1.1.5 Blue Skin