Bobcat 843B problem. Help?????

I'm using my friends 843B bobcat today and two problems arose. first the bucket will no longer lower with the engine running and secondly the bucket won't tilt back with the engine running. I don't have a service manual for this machine but it seems to me that a check-valve or something similar is acting up in the hydraulic system. All the safety systems seem to be operating OK and the pedals have full movement. In fact when you press the pedal too lower the bucket it just shakes like it is trying to raise it. Any thoughts or ideas to try??? :beatsme Thanks Nathan<